Archive for the ‘Gemstones’ Category
Beryl
Posted on: November 8, 2011
Beryl
The mineral beryl is a beryllium aluminium cyclosilicate with the chemical formula Be3Al2(SiO3)6. The hexagonal crystals of beryl may be very small or range to several meters in size. Terminated crystals are relatively rare. Pure beryl is colorless, but it is frequently tinted by impurities; possible colors are green, blue, yellow, red, and white.
Blue to blue-green (aquamarine), dark blue beryl (irradiated), green (emerald), light green (green beryl), greenish yellow to golden yellow (heliodor), peachy pink (peach beryl), pink (morganite), red (red beryl), and colorless (goshenite).
Sourse: North and South America, Northern Europe, East Africa, South Africa, Himalayan Asia, and most notably, Colombia. The beryl family of gemstones is composed of emerald, aquamarine, morganite, heliodor, goshenite, and the rare bixbite (red beryl). These are some of the most valued of all colored gemstones.
Varieties:
Aquamarine and maxixe
Hardness
7.5 – 8.0.
Occurrence
It occurs at most localities which yield ordinary beryl, some of the finest coming from Russia. Brazil, Afghanistan, Pakistan, India, Nigeria and Madagascar. In the United States, aquamarines can be found at the summit of Mt. Antero in the Sawatch Range in central Colorado. In Wyoming, aquamarine has been discovered in the Big Horn Mountains, near Powder River Pass. In Brazil, there are mines in the states of Minas Gerais, Espírito Santo, and Bahia, and minorly in Rio Grande do Norte. The Mines of Colombia, Zambia, Madagascar, Malawi, Tanzania and Kenya also produce aquamarine.
Appearance
Aquamarine is the blue, or blue-green type of beryl. Aquamarine and Bloodstone are the birthstones of the month of March. Clear yellow beryl, such as that occurring in Brazil, is sometimes called aquamarine chrysolite. When corundum presents the bluish tint of typical aquamarine, it is often termed Oriental aquamarine. The deep blue version of aquamarine is called maxixe. Its color fades to white when exposed to sunlight or is subjected to heat treatment, though the color returns with irradiation.
Enhancements
Aquamarine is usually heat treated to remove yellow components thereby producing a purer blue color.
The largest aquamarine of gemstone quality ever mined was found in Marambaia, Minas Gerais,Brazil, in 1910. It weighed over 110 kg, and its dimensions were 48.5 cm (19 in) long and 42 cm (17 in) in diameter
Morganite
Morganite, also known as “pink beryl”, “rose beryl”, “pink emerald”, and “cesian (or caesian) beryl”, is a rare light pink to rose-colored gem-quality variety of beryl. Orange/yellow varieties of morganite can also be found, and color banding is common. It can be routinely heat treated to remove patches of yellow and is occasionally treated by irradiation to improve its color. The pink color of morganite is attributed to Mn2+ ions
Pink beryl of fine color and good sizes was first discovered on an island on the coast of Madagascar in 1910 It was also known, with other gemstone minerals, such as tourmaline and kunzite, at Pala, California. In December 1910, the New York Academy of Sciences named the pink variety of beryl “morganite” after financier J. P. Morgan.
Sourses: Madagascar,Brazil, Elba (Italy),Mozambique,Namibia,Zimbabwe(Rhodesia),Pakistan,U.S.(California)
On October 7, 1989, one of the largest gem morganite specimens ever uncovered, eventually called “The Rose of Maine,” was found at the Bennett Quarry in Buckfield, Maine,USA. The crystal, originally somewhat orange in hue, was 23 cm (9 in) long and about 30 cm (12 in) across, and weighed (along with its matrix) just over 50 lbs (23 kg).
Red beryl
Red beryl
Hardness
7.5.
Occurrence
Wah Wah mountains (Utah), Thomas range (Utah) andMexico. This is one of the rarest minerals. Gem quality material is found only at the Violet claims in the Wah Wah mountains. The mine there produces about one crystal per day. Of these, they are rarely cut into gemstones. Also known as bixbite, but that name is sometimes confused with bixbyite which is a manganese iron oxide.
Appearance
Light pink to a very attractive deep red with a hint of violet. The color of the stone depends on what part of the mine it was found. Like emerald, inclusions are very common in red beryl.
Prices for top quality natural red beryl can be as high as $10,000 per carat for faceted stones. Red beryl has been known to be confused with pezzottaite, also known as raspberry beryl or “raspberyl”, a gemstone that has been found in Madagascar and now Afghanistan – although cut gems of the two varieties can be distinguished from their difference in refractive index. While gem beryls are ordinarily found in pegmatites and certain metamorphic rocks, red beryl occurs in topaz-bearing rhyolites. It formed by crystallizing under low pressure and high temperature from a pneumatolitic phase along fractures or within near-surface miarolitic cavities of the rhyolite. Associated minerals include bixbyite, quartz, orthoclase, topaz, spessartine, pseudobrookite and hematite
Goshenite
Hardness
7.5 – 8.0.
Occurrence
North and South America, Northern Europe, East Africa, South Africa, Himalayan Asia, and most notably, Colombia. The beryl family of gemstones is composed of emerald, aquamarine, morganite, heliodor, goshenite, and the rare bixbite (red beryl). These are some of the most valued of all colored gemstones.
Colorless beryl is called goshenite. The name originates from Goshen, Massachusetts where it was originally discovered. Since all these color varieties are caused by impurities and pure beryl is colorless, it might be tempting to assume that goshenite is the purest variety of beryl. However, there are several elements that can act as inhibitors to color in beryl and so this assumption may not always be true. The name goshenite has been said to be on its way to extinction and yet it is still commonly used in the gemstone markets. Goshenite is found to some extent in almost all beryl localities. In the past, goshenite was used for manufacturing eyeglasses and lenses owing to its transparency. Nowadays, it is most commonly used for gemstone purposes and also considered as a source of beryllium.
The gem value of goshenite is relatively low. However, goshenite can be colored yellow, green, pink, blue and in intermediate colors by irradiating it with high-energy particles. The resulting color depends on the content of Ca, Sc, Ti, V, Fe, and Co impurities.
Golden beryl and heliodor
Hardness
7.5 – 8.0.
Occurrence
North and South America, Northern Europe, East Africa, South Africa, Himalayan Asia, and most notably,Colombia.
Appearance
Lemon yellow to golden in color. Yellow beryl is colored by iron, the golden variety by uranium oxide.
Golden beryl can range in colors from pale yellow to a brilliant gold. Unlike emerald, golden beryl has very few flaws. The term “golden beryl” is sometimes synonymous with heliodor ,but golden beryl refers to pure yellow or golden yellow shades, while heliodor refers to the greenish-yellow shades. The golden yellow color is attributed to Fe3+ ions.[6][7] Both golden beryl and heliodor are used as gems. Probably the largest cut golden beryl is the flawless 2054 carat stone on display in the Hall of Gems, Washington, D.C
Emerald
Hardness
7.5 – 8.0.
Occurrence
Colombia, Brazil, Zimbabwe (Rhodesia), South Africa, Ural mountains (Russia), Zambia, India, Tanzania, Pakistan, Australia, U.S. (Connecticut, Maine, North Carolina), Austria and Norway.
Appearance
Emerald refers to the green variety of beryl. There are however, gem quality green beryls which are not emeralds. All emeralds contain inclusions, which are evidence as to the genuineness of the stone. The name is derived from the Greek word Smaragdos, meaning “green stone”. Emerald is the birthstone of the month of May.
Enhancements
Emerald is usually treated with colorless oil, wax, or natural and synthetic resins into voids to improve appearance. Surface cavities of emerald is commonly filled with a hardened colorless substance. Emerald is also occasionally dyed with dye or colored oil.
Agate(Chalcedony)
Posted on: October 6, 2011
Chalcedony
Chalcedony is a catch all term that includes many well known varieties of cryptocrystalline quartz gemstones. They are found in many colors and color combinations, and in sedimentary, igneous, and metamorphic rocks. Chalcedony has a waxy luster, and may be semitransparent or translucent. It can assume a wide range of colors, but those most commonly seen are white to gray, grayish-blue or a shade of brown ranging from pale to nearly black.Chalcedony includes carnelian, sard, plasma, prase, bloodstone, onyx, sardonyx, chrysoprase, thundereggs, agate, flint, chert, jasper, petrified wood, and petrified dinosaur bone just to name a few of the better known varieties.
Because of its abundance, durability, and beauty, chalcedony was, except for sticks, animal skins, bones, plain rocks, and possibly obsidian, the earliest raw material used by humankind. The earliest recorded use of chalcedony was for projectile points, knives, tools, and containers such as cups and bowls. Early man made weapons and tools from many varieties of chalcedony including agate, agatized coral, flint, jasper, and petrified wood.
The move from using certain items as weapons and tools, to using the same items for ceremonial and personal adornment is very easily made. It was only natural for early man to use his finest looking knife for special occasions or to attach a special lance point or arrowhead to his tunic. In fact, agate and petrified wood may have simply been elevated to gems from common and functional weapons or tools.
Agate is a variety of chalcedony with multi-colored curved or angular banding. Fire agate shows iridescent phenomena on a brown background: iris agate shows exceptional iridescence when light (especially pinpointed light) is shone through the stone. Landscape agate is chalcedony with a number of different mineral impurities making the stone resemble landscape. Although agates may be found in various kinds of rock, they are classically associated with volcanic rocks and can be common in certain metamorphic rocks
Legend:
The stone was given its name by Theophrastus, a Greek philosopher and naturalist, who discovered the stone along the shore line of the river Achates. Colorful agates and other chalcedonies were obtained over 3,000 years ago from the Achates River, now called Dirillo, in Sicily
Formation and characteristics
Most agates occur as nodules in volcanic rocks or ancient lavas where they represent cavities originally produced by the disengagement ofvolatiles in the molten mass which were then filled, wholly or partially, by siliceous matter deposited in regular layers upon the walls. Such agates, when cut transversely, exhibit a succession of parallel lines, often of extreme tenuity, giving a banded appearance to the section. Such stones are known as banded agate, riband agate and striped agate.
In the formation of an ordinary agate, it is probable that waters containing silica in solution—derived, perhaps, from the decomposition of some of the silicates in the lava itself—percolated through the rock and deposited a siliceous coating on the interior of the vapour-vesicles. Variations in the character of the solution or in the conditions of deposition may cause a corresponding variation in the successive layers, so that bands of chalcedony often alternate with layers of crystalline quartz. Several vapour-vesicles may unite while the rock is still viscous, and thus form a large cavity which may become the home of an agate of exceptional size; thus a Braziliangeode lined with amethyst and weighing 35 tons was exhibited at the Düsseldorf Exhibition of 1902. Perhaps the most comprehensive review of agate chemistry is a recent text by Moxon cited below.
The first deposit on the wall of a cavity, forming the “skin” of the agate, is generally a dark greenish mineral substance, like celadonite,delessite or “green earth“, which are rich in iron probably derived from the decomposition of the augite in the enclosing volcanic rock. This green silicate may give rise by alteration to a brown iron oxide (limonite), producing a rusty appearance on the outside of the agate-nodule. The outer surface of an agate, freed from its matrix, is often pitted and rough, apparently in consequence of the removal of the original coating. The first layer spread over the wall of the cavity has been called the “priming”, and upon this base zeolitic minerals may be deposited.
Many agates are hollow, since deposition has not proceeded far enough to fill the cavity, and in such cases the last deposit commonly consists of quartz, often amethyst, having the apices of the crystals directed towards the free space so as to form a crystal-lined cavity, or geode.
On the disintegration of the matrix in which the agates are embedded, they are set free. The agates are extremely resistant to weathering and remain as nodules in the soil or are deposited as gravel in streams and shorelines.
Types of agate
A Mexican agate, showing only a single eye, has received the name of cyclops agate.Included matter of a green, golden, red, black or other color or combinations embedded in the chalcedony and disposed in filaments and other forms suggestive of vegetable growth, gives rise to dendritic or moss agate. Dendritic agates have fern like patterns in them formed due to the presence of manganese and iron oxides. Other types of included matter deposited during agate-building include sagenitic growths (radial mineral crystals) and chunks of entrapped detritus (such as sand, ash, or mud). Occasionally agate fills a void left by decomposed vegetative material such as a tree limb or root and is called limb cast agate due to its appearance.
Turritella agate is formed from silicified fossil Elimia tenera (erroneously consideredTurritella) shells. E. tenera are spiral marine gastropods having elongated, spiral shells composed of many whorls. Similarly, coral, petrified wood and other organic remains or porous rocks can also become agatized. Agatized coral is often referred to as Petoskey stone or agate.
Greek agate is a name given to pale white to tan colored agate found in Sicily back to 400 B.C. The Greeks used it for making jewelry and beads. Even though the stone had been around centuries and was known to both the Sumerians and the Egyptians, both who used the gem for decoration and for playing important parts in their religious ceremonies, any agate of this color from Sicily, once an ancient Greek colony, is called Greek agate.
Another type of agate is Brazilian agate, which is found as sizable geodes of layered nodules. These occur in brownish tones interlayered with white and gray. Quartz forms within these nodules, creating a striking specimen when cut opposite the layered growth axis. It is often dyed in various colors for ornamental purposes.
Certain stones, when examined in thin sections by transmitted light, show a diffraction spectrum due to the extreme delicacy of the successive bands, whence they are termed rainbow agates. Often agate coexists with layers or masses of opal, jasper or crystalline quartz due to ambient variations during the formation process.
Other forms of agate include Lake Superior agate, carnelian agate (usually exhibiting reddish hues), Botswana agate, Ellensburg blue agate, blue lace agate, plume agates, tube agate (with visible flow channels), fortification agate (which exhibit little or no layered structure), fire agate (which seems to glow internally like an opal) and Mexican crazy-lace agate (which exhibits an often brightly colored, complex banded pattern) also called Rodeo Agate and Rosetta Stone depending on who owned the mine at the time.
Aventurine(Quartz)
Posted on: October 6, 2011
Aventurine is a form of quartz, characterised by its translucency and the presence of platy mineral inclusions that give a shimmering or glistening effect termed aventurescence. The most common colour of aventurine is green, but it may also be orange, brown, yellow, blue, or gray. Chrome-bearing fuchsite (a variety of muscovite mica) is the classic inclusion, and gives a silvery green or blue sheen. Oranges and browns are attributed to hematite orgoethite. Due to its grainy structure aventurine has an irregular fracture, so raw, unpolished pieces have a rough surface similar to marble or quartzite. Different from marble, it is not porous, but mostly compact and dense, just like quartzite.
In green aventurine the color is often caused by a chromium-bearing muscovite called “fuchsite”, K(Al,Cr)2AlSi3O10(OH)2, a mineral of the mica group.
Blue aventurine is sometimes labeled blue quartz, which is very confusing. The color is then often caused by dumortierite, (Al,Fe)7O3(BO3)(SiO4)3.
Inclusions:
With the help of 10x loup possible to see the copper outlines.
Aventurine quartz contains small crystal inclusions that reflect light, so that it gives a range of colors to the stone. Green aventurine quartz has platy inclusions of green fuchsite mica. Due to the presence of mineral goethite greenish brown color produced. Other inclusions give bluish white, bluish green or orange.
Hardness:
Because aventurine is a rock, its physical properties vary: its specific gravity may lie between 2.64-2.69 and its hardness is somewhat lower than single-crystal quartz at around 6.5.
Sourses: Brazil, India, Russia, U.S., Japan and Tanzania. A rough specimen of unknown origin, probably India. It is slightly translucent and has a grainy structure. The golden sparkles are caused by tiny pyrite inclusions.
History:
The name aventurine derives from the Italian “a ventura” meaning “by chance”. This is an allusion to the lucky discovery of aventurine glass or goldstone at some point in the 18th century. Although it was known first, goldstone is now a common imitation of aventurine and sunstone. Goldstone is distinguished visually from the latter two minerals by its coarse flecks of copper, dispersed within the glass in an unnaturally uniform manner. It is usually a golden brown, but may also be found in blue or green.
The majority of green and blue-green aventurine originates in India (particularly in the vicinity of Mysoreand Madras) where it is employed by prolific artisans. Creamy white, gray and orange material is found inChile, Spain and Russia. Most material is carved into beads and figurines with only the finer examples fashioned into cabochons, later being set into jewellery.
Andalusite
Posted on: October 5, 2011
Andalusite
Andalusite is best known for its strong pleochroism and its unusual color which is frequently a mixture of both red and green. It is not a color changing gem. It often shows two colors, (red and green) at the same time. Rough crystals will often show green in one direction and red in another. The color is difficult to match on any standard color chart.
Sourses: Andalusite is an attractive and unusual gemstone, first discovered in Andalusia,Southern Spain, after which it is named. It has some similarities with the more expensive alexandrite, as both are strongly pleochroic. It is suitable for use in jewellery as it is quite hard. The fact that it is seldom seen in jewelry is probably because it is quite rare, and most people, even in the jewellery industry, have never heard of it, let alone seen it. Gem quality Andalusite is found inAustralia,Brazil,Russia,Spain,Sri Lanka(Ceylon) and theUnited States. In addition to this, there are some Andalusite deposits in theUnited Kingdom, although the crystals found there are not of gem quality.
Evaluation :
Andalusite is rated at 6.5 – 7.5 on the Moh’s Scale of Hardness, making it a durable gemstone, suitable for every day wear.
Andalusite is found in brown, brownish-green, gray, green, greenish-brown and red. Andalusite gemstones display pleochrism, meaning that a single stone displays different colorations, depending on the angle the stone is viewed at. In addition to this, one variety of Andalusite commonly displays a cross (crucifix), which is present due to natural inclusions. This variety of Andalusite (Chiastolite), is often set in a pendant and is particularly sought after in staunchly Catholic countries due to the symbolism of the cross.
Common Cuts :
The color displayed by an Andalusite stone is often dictated by the way it is cut. Andalusite is commonly cut into Emerald, Marquise, Oval, Round and Square shapes. Emerald, Marquise and Oval cuts tend to make the stone display one central color, with a differing color at each end, whereas Round and Square Cuts commonly create a mosaic effect, blending different colors together beautifully.
Routine Enhancements :
Whilst Andalusite can be heat-treated in order to improve color, this is rarely needed.
Luster is vitreous
Cleavage is good in two directions.
Fracture is splintery to subconchoidal.
Other Characteristics: dark inclusions produce cruciform shapes in the variety chiastolite. Index of refraction is 1.632-1.638.
Color
Andalusite is a gem that is capable of displaying different colors at the same time. This is different from the color changing gems like Alexandrite and the color changing garnets, because the different colors on Andalusite are displayed at the same time. This is called pleochroism, which is caused by the double refraction of light in a stone. When the two rays of light pass through the stone, they travel at both different angles & speeds, and display different colors of the spectrum. This allows a person to see different colors on the stone, when viewed from different angles, in the same light source. For the color changing stones like Alexandrite and color change garnets, it is necessary to have two different light sources to be able to see the color change.
Typical colors for andalusite are green, brown, red, greenish-brown, brownish-green. Its pleochroic colors are red, green and yellow.
Because of the pleochroism, the color of an andalusite can be affected considerably by the direction in which it is cut.
Our photograph is disappointing and deceptive. The actual stone is a pleasant greenish brown to red. We used flash lighting with a digital camera, followed by software adjustment of the lighting levels, and the effect was to make the stone appear quite a dull brownish color.
Star Andalusite or Chiastolite
An impure variety of andalusite known as chiastolite contains carbonaceous inclusions in a cruciform arrangement. These are cut as cabochons and polished for use as amulets in many countries, largely because of the symbolism of the cross.
Ametrine
Posted on: October 5, 2011
Ametrine is a Silicon Dioxide and is a member of the Quartz family. The unusual color variation in Ametrine is due to the presence of iron impurities in different oxidation states within the crystal structure
History:
The name Ametrine was coined for a member of the Quartz family which displays a combination of both Amethyst and Citrine.
Natural Ametrine first arrived in the market in 1980 when it was discovered at the Anhai mine inBolivia. This mine became well- known when a Spanish conquistador received it as a dowry when he married a princess from the Ayoreos tribe in the seventeenth century.
Ametrine is said to aid meditation, to calm and relieve tension, and dispel negativity . It is also believed to have all the metaphysical properties of both Amethyst and Citrine:
Amethyst has been thought to protect against intoxication and to help maintain a sober and serious mind. Amethyst opens and activates the crown chakra, the third eye chakra, and can also open the heart chakra. Amethyst can be used to fight a number of disorders including headaches, insomnia, hearing disorders, heart disorders, digestive system disorders, and has even been thought to help stabilize mental disorders. Amethyst also works emotionally and spiritually by providing patience, balance, calmness, and peace
It has been said that Citrine helps to manifest your goals and keeps the wearer cheerful. In ancient times, Citrine was carried as protection against snake venom and evil / impure thoughts. Citrine does not absorb negative energies but rather dissipates and transmutes them, which is why this stone is good for clearing your aura. It attracts abundance, prosperity, and success, and because of this Citrine has been nicknamed the “success stone.” Citrine stimulates the solar plexas and third eye chakras, promoting stamina and activating intuition. It can also help to overcome sleep related problems such as insomnia and nightmares. Physically it is said to help with poor blood circulation, digestion, allergies, and an aid to curing life-threatening diseases.
Sourses:
Until very recently, the world’s only source of this bicolored natural quartz is the Anahi Mine located in the jungles ofBolivia. It is rumoured that the mines where first discovered by native Indians in the seventeenth century. The Bolivian government declared the land a state reserve and built a fortress near the mine entrance. Despite its remote location, ametrine (as well as natural amethyst and citrine) made its way across the border toBrazil. These goods were then sold as Brazilian products. This caused a change in the government inBoliviain 1989. The rights to the mine were sold, and during the past decade, these collectible gems became available on the domestic marketplace.
*Miners in the Brazilian state ofBahiaare finding small amounts of this combination amethyst/citrine.
Ametrine is among an elite group of gems, because as of now there is just one source of this treasure in the world. You should add an ametrine to your collection now, since its future availability is uncertain at best.
Medicine: Ametrine is very helpful in getting rid of depression. This leads to inner peace and tranquility.
Many believe that it contains the powers of amethyst and citrine in one stone, making it a very powerful money stone as well as an excellent via to higher psychic awareness and spiritual enlightenment.
Evaluation :
Ametrine is rated at 7 on Moh’s Scale of Hardness and is a durable gemstone that lacks cleavage. Ametrine combines the appeal of both the violet-purple Amethyst and the yellow-orange Citrine in one bi-colored gemstone. Ametrine gemstones can be found displaying an equal share of the Amethyst and Citrine as well as a blended color affect, displaying attractive shades of rosy gold and mauve. The most important aspects to consider when viewing an Ametrine is the depth and intensity of the colors and the distinctiveness of the separation. The creativity of the cut should also be taken into account.
Routine Enhancements :
Most of the Ametrine found on the market today is actually heat-treated Amethyst.
Availability :
Ametrine rarely occurs naturally and most of the Ametrine found on the market today is heat-treated Amethyst. For Ametrine to occur naturally, the iron impurities in the quartz have to be affected in different ways. For example, both sides of the stone must be subjected to two slightly different temperatures during the crystallization process of the Quartz for Ametrine to form. The only two known sources of natural Ametrine is the Anahi mine inBolivia and theRio Grande do Sul mine inBrazil. Although this gemstone is rare it is relatively inexpensive.
Cleaning :
Ametrine is best cleaned using warm soapy water and a soft brush. Though there is no special care required,
Alexandrite(Chrysoberyl)
Posted on: October 5, 2011
History:
The name chrysoberyl is derived from the Greek words chrysos and berullos, meaning “golden” and “gem crystal“. Despite the similarity of their names, chrysoberyl and beryl are two completely different gemstones. Members of the beryl group include emerald, aquamarine, and morganite while members of the chrysoberyl group include chrysoberyl, cymaphane (cat´s eye) and alexandrite. Beryl is a silicate with chemical composition Be3Al2(SiO3)6 and chrysoberyl is an oxide with composition BeAl2O4. Although both beryl and chrysoberyl contain beryllium, they are separate gemstone species unrelated in any other way. Beryl crystallizes hexagonally while chrysoberyl crystallizes in orthorhombic arrangements. Chrysoberyl will crystallize at higher temperatures than beryl. With cooling temperatures and increasing water activity, it will react with K-spar to form beryl + muscovite. Thus after chrysoberyl crystallizes in Be-rich pegmatites that intrude ultramafic hosts, tectonometamorphic events often result in metamorphic overprint. During crystallization of the pegmatite, much beryllium can be accommodated into the common rock-forming minerals of the pegmatite leaving little of the metal to form minor amounts of either beryl or chrysoberyl.
Chrysoberyl was discovered in 1789 and described and named by Abraham Gottlob Werner (1749-1817), in 1790. Werner worked at the Freiberg School of Mining from 1790-1793 and was well known as one of the most outstanding geologists of his time. He is best known today as the loser in the battle of the Neptunists and Vulcanists that raged in the 1780s. Werner theorized that the features of the earth´s crust had been laid down when a primitive ocean subsided and this debate led to the birth of modern geology. Werner developed techniques for identifying minerals using human senses and his practical classification system appealed to a broad audience. The stone scapolite, also known as Wernerite, was named in his honor.
Formation:
Chrysoberyl was formed as a result of pegmatitic processes that occurred at least 250 million years ago. High temperatures and pressures from the outer layers of the earth´s mantle forced molten magma towards the surface. As the main magma body cooled, water originally present in low concentrations became more concentrated in the molten rock because it could not be incorporated into the crystallization of the localized minerals. Consequently, the remaining portion of the molten magma was water rich. It was also rich in rare elements and silica that still had not solidified. When this water-rich magma was expelled in the final stages of the crystallization, it solidified in cracks and crevasses to form a pegmatite.
If the pegmatite magma was rich in beryllium, crystals of beryl and chrysoberyl could form but for alexandrite to form, some chromium would also have had to be present. Since beryllium and chromium are extremely rare elements in rocks, this is only process which could have concentrated these unusual elements in an environment where crystallization could occur.
The high water content of the magma made it possible for the crystals to grow quickly, so pegmatite crystals are often quite large and this is of course important for gem specimens. Chrysoberyl is always accompanied by quartz. It occurs in granite pegmatites and mica schists and in contact with metamorphic deposits of dolomitic marble. It is also recovered from river sands and gravels in alluvial deposits with corundum, spinel, garnet and tourmaline.
Chrysoberyl is normally yellow, yellow-green, or brownish with its color being caused by the presence of iron. Spectroscopic analysis will usually reveal a strong band where the violet takes over from the blue. As the color darkens from bright yellowish-green to golden-yellow to brown, this band increases in strength. When the stone has a strong color, two additional bands can be seen in the green-blue. The most common inclusions are liquid-filled cavities containing three-phase inclusions. Stepped twin planes may be apparent in some cases. Some very rare minty bluish-green chrysoberyls from Tanzania owe their color to the presence of Vanadium. These stones are quite rare and exceptional specimens can command prices as high as alexandrite.
All varieties of chrysoberyl are hard and tough, with a high luster. Because of its high degree of hardness (8.5), chrysoberyl can be highly polished with very flat facets and sharp facet junctions. Uncut crystals of chyrsoberyl may display cyclic twins called trillings. These crystals appear hexagonal but are the result of a triplet of three twins, with each twin taking up 120 degrees of the cyclic trilling.
Chrysoberyl is relatively unknown in its own right due the confusion between chrysoberyl and beryl and the alexandrite variety is much more widely recognized. For such a hard and durable material, yellow chrysoberyl is relatively obscure and the low prices don´t seem to reflect its utility as a gemstone. The only natural stones harder than chrysoberyl are corundum and diamond.
There are two main varieties of chrysoberyl: cat´s eye or cymophane, and alexandrite. Although yellow chrysoberyl was referred to as chrysolite during the Victorian and Edwardian eras, that name is no longer used in the gemological nomenclature. Chrysoberyl that does not show a color change or a cat´s eye is known simply as chrysoberyl.
Translucent yellowish chatoyant chrysoberyl is called cymophane or cat’s eye. Its name is derived from the Greek words cyma and phanes, meaning “wave” and “appearance”. Microscopic needle-like inclusions inside the stone reflect a streak of light known as a cat´s eye. The cat’s eye’s inclusions are aligned parallel to the crystallographic axis and they are always cut as cabochons with the fibrous need-like inclusions running across the narrow part of the stone as this is the only way to display the effect properly. The effect becomes most apparent under a spotlight or direct sunlight. A thin bright band of light will appear and open and close as the stone is rotated — hence the eye like effect. This phenomenon is also known as chatoyancy, which comes from the French chat for cat, and oeil for eye. Chrysoberyl lacking the silky inclusions required to produce the cat´s eye effect is usually faceted. An alexandrite cat´s eye is a chrysoberyl cat´s eye that changes color. Although other minerals including tourmaline, beryl, scapolite and quartz may also display the cat´s eye effect, these stones are referred to as tourmaline cat´s eyes or quartz cat’s eyes etc., and only chrysoberyl is referred to as “cat’s eye” with no other designation.
Milk and honey is a term commonly used to describe the color of the best cat’s eyes. The effect refers to the sharp milky ray of white light normally crossing the cabochon as a center line along its length and overlying the honey colored background. The honey color is considered to be top by many gemologists but the lemon yellow colors are also popular and attractive. Cat´s eye material is found as a small percentage of the overall chrysoberyl production wherever chrysoberyl is found.
Alexandrite is the variety of chrysoberyl that displays a color change as a function of the light source. It is the presence of chromium that is responsible for the color change in alexandrite. The two colors are usually blue-green in daylight and purplish-red under incandescent light. Stones with a weak change or better are identified as alexandrite while stones with a faint change should be identified as chrysoberyl.
Alexandrite results from the small scale replacement of aluminium by chromium in the oxide resulting in alexandrite´s characteristic green to red color change effect. Its rarity is due to the requirements for two kinds of minerals, – one providing aluminium and beryllium and the other providing chromium oxide.
Only chrysoberyl displaying a distinct change of color should be designated as alexandrite. This means that chrysoberyl and alexandrite can be difficult to differentiate. Since stones with a weak change may be called alexandrite or chrysoberyl, the determination can be subjective. As the color change in alexandrite is due to the presence of chromium, and the color of yellow or brown in ordinary chrysoberyl is due to the presence of iron, spectroscopic examination will reveal these differences and help with identification. Chrysoberyl usually shows no fluorescence. The red fluorescence of alexandrite is evident using the “crossed filter” method.
Common Cuts :
Alexandrite is most usually cut into Cushion and Oval shapes, but Emerald and Round cuts are also quite common.
Routine Enhancements :
There are no known treatments for Alexandrite.
Care & Cleaning :
Alexandrite can be cleaned in warm, soapy water and can also be cleaned in alcohol or commercially available products. Ultrasonic and steam cleaning processes are generally considered to be safe but should these methods be used, they should really be undertaken by suitably qualified jewelers. Alexandrite should be kept away from prolonged exposure to excessive heat as this can effect the stones color change effect.
African Jade
Posted on: September 27, 2011
Jade is an ornamental stone. The term jade is applied to two different metamorphic rocks that are made up of different silicate minerals:
- Nephrite consists of a microcrystaline interlocking fibrous matrix of the calcium, magnesium-iron rich amphibole mineral series tremolite (calcium-magnesium)-ferroactinolite (calcium-magnesium-iron). The middle member of this series with an intermediate composition is called actinolite (the silky fibrous mineral form is one form of asbestos). The higher the iron content the greener the colour.
- Jadeite is a sodium- and aluminium-rich pyroxene. The gem form of the mineral is a microcrystaline interlocking crystal matrix.
Nephrite can be found in a creamy white form (known in China as “mutton fat” jade) as well as in a variety of green colours, whereas jadeite shows more colour variations, including blue, lavender-mauve, pink, and emerald-green colours. Of the two, jadeite is rarer, documented in fewer than 12 places worldwide. Translucent emerald-green jadeite is the most prized variety, both historically and today. As “quetzal” jade, bright green jadeite from Guatemala was treasured by Mesoamerican cultures, and as “kingfisher” jade, vivid green rocks from Burma became the preferred stone of post-1800 Chinese imperial scholars and rulers. Burma (Myanmar) and Guatemala are the principal sources of modern gem jadeite, and Canada of modern lapidary nephrite. Nephrite jade was used mostly in pre-1800 China as well as in New Zealand, thePacificCoast andAtlanticCoasts of North America, Neolithic Europe, and south-eastAsia. In addition toMesoamerica, jadeite was used by Neolithic Japanese and European cultures.
Chemical Symbol:
African Jade is a complex Calcium Aluminum Silicate. Its bright green coloration is due to traces of chromium.
History :
African Jade is mined in South Africa, and for this reason alone receives its name. It is occasionally referred to as Transvaal Jade.
Medicine:
It is considered to bring good luck, wealth, relaxation, and can improve the wearers response during a crucial situation. African Jade is also thought to be an important aid in business relationships and can help in keeping long distance relationships intact.
African Jade is a gemstone of general healing abilities and is considered to specifically aid kidney and skin related disorders and diseases.
Common Cuts:
African Jade can be cut into a variety of shapes/cuts with oval, round, and cushion cuts being the most common. African Jade has also traditionally been used in tribal carvings and sculptures.
Routine Enhancements:
There are no known enhancements for Agrican Jade.
Evaluation:
African Jade is a tough, opaque stone that lacks cleavage and is rated at 6.5 to 7.5 on Moh’s Scale of Hardness. African Jade has a vitreous luster and is most often a forest green to a greyish green, but may also be multi-colored and display shades of pink and white.
Amber
Posted on: September 27, 2011
Chemical Make-up :
Amber is a mixture of Succinic acid, numerous resins and volatile oils. In addition to this, Amber also contains Hydrogen Sulphide (H2S).
Used by man even before the ice age, natural amber gemstone can be categorized as an organic gem material of vegetable origin. Amber is not a mineral, but time-hardened fossilized resin of the species of pine called Pinus Succinisera. These trees grew in forests around 45 million years ago, in the European main land known to us as the Baltic region today!
The early Germans called this Baltic amber by the name of Bernstein, due to the sweet smell it emitted when burnt. The Greeks called it Elektron due to its properties of developing static electricity when rubbed. Amber is known as Kerba in the local markets inIndia.
History:
Amber is one of the three organic gemstones and is actually made-up of the fossilized resin of pine trees from between twenty and sixty million years ago. Amber produces static electrivity when rubbed and for this reason Amber was known as elektron to the ancient Greeks, which translates very simply as “electron”, and refers to the negatively charged particles in electricity. In the Middle Ages, Amber was known as bernstein, or “burn stone” in Germany, as powdered Amber was commonly burnt as an incense.
Amber helps to remove blockages in the flow of energy throughout the body and therefore works as an aid to strengthening the body. Amber has traditionally been used to bring protection, strength, love, luck and healing to the wearer. Amber is an excellent healing stone as it takes negative energy and transforms it into positive energy. Amber also helps to calm stressed nerves and to bring about humour and joy as well as acting as a guard against impotency and as an aid to fertility. Amber opens the crown and solar plexus chakras, thereby helping to increase intellect and confidence.
Amber is a hydrocarbon (C10 H 16 O). It is a complex mixture of several resinous bodies, succinic acid, volatile oil and also contains some amount of hydrogen sulfide (H2S). Its specific gravity is 1.08 and refractive index is 1.54. It`s hardness on Mohs scale is 2 to 2.5, and is sectile (i.e it can be sliced or shaved). The Burmese amber is said to be hardest and the Dominican, the softest.
Sources :
Gem quality amber gemstone is mainly found in the Baltic Sea region. The other regions where amber is found include Myanmar (Burma), Dominican Republic, Germany, Rumania, Sicily, North America, Russia and Malaysia. Some of the popular jewelry is comprised of Celtic amber jewelry and blue amber jewelry. However, a honey colored amber ring is always sought after by many buyers – especially if it is a carved amber ring. Amber stone rings and amber mala are also very popular. Due to the history of amber gemstone in the Baltic region, Baltic amber jewelry is very highly prized. Baltic amber jewelry like necklaces, pendents made out of amber beads fetch a good price in the market. There are many markets where wholesale Baltic amber jewelry is traded and sold worldwide. Amber jewelry is usually made using silver, rather than gold because it gives the stone a very unique look. Small and large stones are fashioned into silver pendants and sold all over the world. The markets are full of various kinds of jewelry items such as amber earrings, amber bracelets, amber bead necklaces, and even amber stud earrings. A small piece of amber stone can be fashioned into a delicate silver wire wrap amber pendant. Depending on the design and the color, a number of great looking custom jewelry items can be created out of amber stones. These can make for wonderful gift items.
The color of amber fossil varies from yellow to dark brown to almost black. Very rarely this gem may be found in green and blue-gray colors and hence green amber can be very rare. In addition, it is dyed in many colors like green, blue, pink etc. The color of this gem denotes the area from where it has originated. Baltic amber is yellow, Sicilian is reddish yellow, Rumanian is brown and Burmese is yellow to reddish-brown.
Evaluation :
Amber is rated at 1.5 – 2.5 on the Moh’s Scale of Hardness, making Amber a very soft gemstone that may not immediately bw deemed suitable for jewelry purposes. However Amber is often used in all kinds of jewelry applications and providing that you take the correct precautions and wear your Amber with care, there is no reason why it should not form part of your jewelry collection.
Amber is found in a number of colors including, Black, Blue, Brown, Green,Orange, Red, White and Yellow, with rich golden Yellow being the color that most people associate with the gemstone Amber. The most valuable Amber is translucent and unlike other gemstones, inclusions actually enhance its rarity and beauty. These inlcusions are usually entrapped insects from thousands and thousands of years ago. The more complete the specimen of trapped insect / inclusion is, the more the value of the Amber increases.Amber is generally speaking a very affordable gemstone, but the very best examples can reach tens of thousands of dollars per carat.
Amber gemstone is usually cut as beads and cabochons. Many times it is just polished and used in its crude rough shape. Opaque gems of big sizes are mostly used in carvings. Gems with inclusions are mainly fashioned as cabochons. Amber beads are popular choice for use in necklaces and bracelets. Amber gemstone is usually sold by piece and not by weight.
Clarity:
Inclusions in amber gemstone actually serve to increase its value. Its transparency may vary from transparent to semi-translucent to opaque.
During the process of fossilization, a variety of flora and fauna tend to remain trapped in the amber resin and eventually become an integral part of the final gem i.e. amber. Flora like wood fragments, leaves, flowers, larvae, caterpillars, bees, flies, butter flies, spiders and even land snails and other plant parts and ferns are also found in.Identification of Amber from its Imitation
Natural Amber gemstone is easily distinguished from its plastic imitations. Natural Amber gemstone floats in saturated salt solution but plastics sink, as it has a very low specific gravity – near 1.08. Also if heated or a contact with hot point, plastics give off an acrid odour, in contrast to the resinous smell of amber. An amber imitation called amberdan (and sometimes as cultured amber) has properties fairly near natural amber. Its refractive index is about 1.56 (natural amber is 1.54) and its specific gravity is 1.23, also well above that of natural amber. The hot point gives an odor at once reminiscent of plastic and amber, suggesting a natural resin with a plastic binder.
Natural Amber gemstone is readily distinguished from more recent resins by the simple test. If it is dipped in ether and left for a few minutes, it is unaffected. While the recent resins soften.
Unlike natural amber gemstone, pressed amber is made by mixing bits of amber with linseed oil and compressing it. It is also softened by ether and has elongated bubbles and distinct flow structure. The bubbles in natural amber are spherical.
Azurite Malachite
Posted on: September 26, 2011
Chemical Symbol :
Azurite – Cu3(CO3)2(OH)2
Malachite – Cu2CO3(OH)2
Chemical Make-up :
Azurite-Malachite is made up of Azurite and Malachite banded together. Both gemstones are made up of basic copper carbonate minerals. The blue of azurite is exceptionally deep and clear, and for that reason the mineral has tended to be associated since antiquity with the deep blue color of low-humidity desert and winter skies. The modern English name of the mineral reflects this association, since both azurite and azure are derived via Arabic from the Persian lazhward (لاژورد), an area known for its deposits of another deep blue stone, lapis lazuli (“stone of azure”).
History:
There is not 100% agreement regarding the exact origins of the name Azurite, but the two most widely accepted opinions are that the word Azurite is derived from either the Arabic word azul, or the Persian word lazhward, both of which translate to the color blue.
Malachite gets its name from the Greek word moloche, meaning mallow, which makes reference to Malachite’s green color.
Azurite-Malachite was previously said to help cure convulsions and to act as a local anaesthetic. Malachite was cited as a natural healer and Azurite helped the wearer to listen to themselves and to unlock previously hidden talents.
In some ancient civilizations Malachite was thought to be a protection from evil if worn as jewelry.
Malachite was a popular decorative stone in Czarist Russia, and was used to make the columns of St. Isaac’s Cathedral in Leningrad. Malachite also adorned many walls and even whole rooms of other religious and public buildings.
The European name Chessylite is from a famous Azurite locality inChessy,France.
Azurite-Malachite promotes wisdom, increases psychic awareness / ability by unblocking mental blocks and dissipating negativity. Azurite-Malachite enables the wearer to look inside themselves with greater ease and understanding. Azurite is associated with the Third Eye and Throat Chakras and considered an aid to meditation.
Sources :
There are known Azurite-Malachite deposits in Australia, Chile, England, France, Germany, Greece, Mexico, Morocco, Namibia, United States (Arizona, Pennsylvania, North Carolina and Utah), and Zaire.
Evaluation :
Azurite-Malachite is rated at 3.5 – 4 on the Moh’s Scale of Hardness, meaning that this gemstone is best suited to brooches, earrings and pendants, although it is often set in rings.
Cleaning :
Azurite-Malachite is a soft stone and particularly susceptible to acids, even in diluted form. The best way therefore to clean your Azurite Malachite is with warm, soapy water and a soft cloth. Always be sure to store your Azurite- Malachite jewelry away afrom and seperate to harder gems / jewelry which may scratch this softer stone.
Jewelry
Azurite is used occasionally as beads and as jewelry, and also as an ornamental stone. However, its softness and tendency to lose its deep blue color as it weathers limit such uses. Heating destroys azurite easily, so all mounting of azurite specimens must be done at room temperature. The intense color of azurite makes it a popular collector’s stone. However, bright light, heat, and open air all tend to reduce the intensity of its color over time. To help preserve the deep blue color of a pristine azurite specimen, collectors should use a cool, dark, sealed storage environment similar to that of its original natural setting.
Apatite
Posted on: September 26, 2011
Apatite is infrequently used as a gemstone. Transparent stones of clean color have been faceted,and chatoyant specimens have been cabochon cut. Chatoyant stones are known as cat’s-eye apatite. transparent green stones are known as asparagus stone, and blue stones have been called maroxite. Crystals of rutile may have grown in the crystal of apatite so when in the right light, the cut stone displays a cat’s eye effect.
Chemical Symbol :
Ca5(PO4)3(OH,F,Cl)
Chemical Make-up :
Apatite is made up of basic Fluoro-Calcium, Chloro-Calcium and Hydroxyl
Phosphate minerals.
History:
The word Apatite is derived from the Greek word apate, meaning to decieve. This was primarily due to the fact that Apatite was often mistaken for rarer, more valuable gemstones such as Beryl, Olivine and Peridot. Apatite falls into two categories, Chlor-Apetite (Chloro-Calcium), and Flour-Apetite (Flouro—Calcium).
Apatite enhances the wearers learning abilities, self-confidence and creativity. In addition to this, Apatite is an aid to achieving a deeper state of meditation and to increasing insightfulness. Apatite eases hypertension and decreases hunger, or “appetite”. In addition to this, Apatite is said to be a good gemstone for unblocking any of the chakras.
Care & Cleaning :
Apatite is particularly sensitive to abrasives, chemicals, heat, ammonia and acids. Ultrasonic cleaners and steamersshould also be avoided. Apatite is best cleaned with warm, soapy water and a soft cloth. Apatite
jewelry should be stored on its own in a lined jewelry box, away from harder jewelry, which may cause
scratches or abrasions.
Evaluation :
Apatite is rated at 5 on the Moh’s Scale of Hardness. Apatite can be worn every day in brooches, earrings and pendants, but it is generally considered too soft to be worn daily in a ring.
Apatite can be found in many colors, including, blue, brown, colorless, green, pink, purple, red, violet and yellow. There is also a “Cat’s Eye” Apatite. Brown, green and yellow are the commonly occuring colors, with blue, colorless, pibk, red, violet, and the most recently discovered neon blue-green examples being the rarest and therefore most valuable Apatite colors.
When buying Apatite gemstones, the two most impotant factors to consider are color and clarity. Gemstones with good color saturation and few inclusions are inherently more valuable and command higher per Carat prices.
Sourses: There are known Apatite desposits in Algeria, Austria, Burma (Myanmar), Brazil, Canada, Egypt, Germany, India, Israel, Kenya, Madagascar, Mexico, Morocco, Norway, Portugal, Russia, Spain, Sri Lanka (Ceylon), Sweden, Tunisia and the United States (California, Utah, Nevada, Idaho, Wyoming and Montana).
Apatite is the most common phosphate mineral, and is the main source of the phosphorus required by plants. The bones and teeth of most animals, including humans, are composed of calcium phosphate, which is the same material as Apatite.
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