Sunday, September 23, 2012
Friday, August 19, 2011
Kunzite
History and General Information of Natural Kunzite Gemstone
Like most natural gemstones, which are named after the person who discovered them or else researched it, kunzite gemstone is named after George Frederick Kunz (1856 – 1932), a New York jeweler. This gemstone was first discovered in Pala District of San Diego County in California in 1902. It is a fairly young gem, because it was discovered only a century back, and only now is it being seen in popular jewelry. The stone is valued for its pink color, which ranges in hue from a light pink to a deep lilac (bluish purple).
Kunzite gemstone belongs to the group of gems from the mineral spodumene. Due to its extreme fragility, kunzite is rarely used in jewelry where small pieces are needed. Instead, pendants are fashioned out of it and it is used as ornamentation for decorative objects. Gem kunzite is also known as the evening stone and the reason behind it is its susceptibility to lose color when worn in sunlight, for long periods of time.
Hematite
Hematite
Hematite is a compact form of iron oxide. It varies considerably in compactness and form. Its hardest and most compact form is what gets used in jewelery as a gemstone. This is black, and is normally found in massive form as nodules, usually kidney shaped (reniform), sometimes known as kidney ore.
When crushed or powdered it becomes red, and its less compact forms are also red, streak tests are also red.
The compact black forms have specific gravities and hardness at the higher end of the range. The softer forms are used as red pigments, and as jeweler's rouge.
Misnomers
Because of its red streak, it is sometimes known in German as blutstein (bloodstone), but this term is better avoided because of confusion with bloodstone, a variety of chalcedony.
color
Gem quality hematite is black, although some describe it as blue-black.
Sources
One of the main sources is Cleator Moor in Cumbria, England, but it is also found in Elba, the Swiss alps, Germany, Scandinavia, and the USA.
It is carved or polished in Idar Oberstein, but much is now processed in places with lower labour costs.
Imitations
Hematite is sometimes used as beads to imitate black pearls. There are also imitations of haematite, at least one of which produces a red streak.
Hematite in Jewelery
Hematite is often carved as a cameo or sealstone, and is very commonly seen in gent's rings with a crude intaglio carving of a helmeted warrior's head. It is also used as a faceted stone when it resembles black diamond. Because it is opaque, only the top of the stone is faceted, the bottom of the stone is usually left flat.
Hematite is a compact form of iron oxide. It varies considerably in compactness and form. Its hardest and most compact form is what gets used in jewelery as a gemstone. This is black, and is normally found in massive form as nodules, usually kidney shaped (reniform), sometimes known as kidney ore.
When crushed or powdered it becomes red, and its less compact forms are also red, streak tests are also red.
The compact black forms have specific gravities and hardness at the higher end of the range. The softer forms are used as red pigments, and as jeweler's rouge.
Misnomers
Because of its red streak, it is sometimes known in German as blutstein (bloodstone), but this term is better avoided because of confusion with bloodstone, a variety of chalcedony.
color
Gem quality hematite is black, although some describe it as blue-black.
Sources
One of the main sources is Cleator Moor in Cumbria, England, but it is also found in Elba, the Swiss alps, Germany, Scandinavia, and the USA.
It is carved or polished in Idar Oberstein, but much is now processed in places with lower labour costs.
Imitations
Hematite is sometimes used as beads to imitate black pearls. There are also imitations of haematite, at least one of which produces a red streak.
Hematite in Jewelery
Hematite is often carved as a cameo or sealstone, and is very commonly seen in gent's rings with a crude intaglio carving of a helmeted warrior's head. It is also used as a faceted stone when it resembles black diamond. Because it is opaque, only the top of the stone is faceted, the bottom of the stone is usually left flat.
Tuesday, June 2, 2009
Garnet
Introduction
Garnet is a naturally occurring gemstone.Its name comes from Latin granatus meaning seed, because it often resembles small round seeds when found in its matrix rock.Rather than a single gemstone, garnet is a family of related minerals, some of which occur as gemstones.Each has a common crystal structure, and a similar chemical composition.The popular understanding of garnet is as an inexpensive dark red stone. Because it is relatively common and inexpensive, it is often thought of as "only garnet", and as being inferior.This bias extends to other rare and attractive forms of garnet.
Colour
Garnet occurs naturally in a large range of colours including: red, orange, brown, green, yellow, and brown.
Two Families of Garnet
There are two main theoretical groups or "families" of garnet:- pyrope, almandite, spessartite, which are all (metal) aluminium silicates, anduvarovite, grossularite, andradite, which are all calcium (metal) silicates.In practice, there are probably very few garnets with the precise pure chemical composition shown for their type, almost all garnets are of mixed types, where one type is partially replaced by another type.
Trade Terminology
In the trade, gem dealers hardly ever refer to their stock as "pyrope" or "almandite". Instead, they will often refer to "brown" or Indian garnets. As we have stated, very few, if any, pure "types" of garnet occur, most specimens approximate to a particular type.Brown and purpleish "Indian" garnets will usually be towards the pyrope end of the pyrope-almandite axis.Reddish "African" garnets will usually be towards the almandite end of the pyrope-almandite axis.Rhodolite garnets are usually about midway along the pyrope-almandite axis.
Demantoid Garnet
Demantoid garnet is a rare and beautiful bright grass green sub-variety of andradite garnet. It appears to have first been discovered around 1892 in the Bobrovka area of Russia.The Bobrovka is a small tributary of the River Tschussowaja in the Sissersk region on the western side of the Ural Mountains.It was at first thought to be emerald, which is found nearby, and has been erroneously called "Uralian emerald".The name demantoid means diamond-like, because it has a very high adamantine lustre, and a colour dispersion higher than diamond. The only disadvantageous property of demantoid is its low hardness figure at about 6.5 Moh. It is the softest of the garnets, and is more suitable for use in brooches, pendants, or ear-rings, rather than rings, because of this.The brilliant colour of demantoid garnet is due to partial replacement of the silicate by chromic oxide.A diagnostic characteristic of demantoid is the inclusion of radiating fibres of byssolite (asbestos) fibres in a pattern described as a horse-tail. There is no other green stone which shows this feature.In late Victorian times, and early in the twentieth century, demantoid became a very sought after stone. It commanded high prices because it has never been available in large quantity. In recent decades, it has been unobtainable as newly mined stones, and has only been available from antique jewellery.Recently, small finds have again been made in Russia, and a small quantity of fine quality stones have recently come onto the market. Gemstone lovers wishing to acquire a piece of demantoid garnet should take this opportunity to do so. If the current seams of demantoid run out, there may be another century without new stocks of demantoid becoming available.
Tsavolite Garnet
Tsavolite, previously called tsavorite, is a bright green variety of grossular garnet, its colour being induced by the presence of chromium.
Two Families of GarnetThere are two main theoretical groups or "families" of garnet:- pyrope, almandite, spessartite, which are all (metal) aluminium silicates, anduvarovite, grossularite, andradite, which are all calcium (metal) silicates.In practice, there are probably very few garnets with the precise pure chemical composition shown for their type, almost all garnets are of mixed types, where one type is partially replaced by another type.
Trade TerminologyIn the trade, gem dealers hardly ever refer to their stock as "pyrope" or "almandite". Instead, they will often refer to "brown" or Indian garnets. As we have stated, very few, if any, pure "types" of garnet occur, most specimens approximate to a particular type.Brown and purpleish "Indian" garnets will usually be towards the pyrope end of the pyrope-almandite axis.Reddish "African" garnets will usually be towards the almandite end of the pyrope-almandite axis.Rhodolite garnets are usually about midway along the pyrope-almandite axis.
Demantoid GarnetDemantoid garnet is a rare and beautiful bright grass green sub-variety of andradite garnet. It appears to have first been discovered around 1892 in the Bobrovka area of Russia.The Bobrovka is a small tributary of the River Tschussowaja in the Sissersk region on the western side of the Ural Mountains.It was at first thought to be emerald, which is found nearby, and has been erroneously called "Uralian emerald".The name demantoid means diamond-like, because it has a very high adamantine lustre, and a colour dispersion higher than diamond. The only disadvantageous property of demantoid is its low hardness figure at about 6.5 Moh. It is the softest of the garnets, and is more suitable for use in brooches, pendants, or ear-rings, rather than rings, because of this.The brilliant colour of demantoid garnet is due to partial replacement of the silicate by chromic oxide.A diagnostic characteristic of demantoid is the inclusion of radiating fibres of byssolite (asbestos) fibres in a pattern described as a horse-tail. There is no other green stone which shows this feature.In late Victorian times, and early in the twentieth century, demantoid became a very sought after stone. It commanded high prices because it has never been available in large quantity. In recent decades, it has been unobtainable as newly mined stones, and has only been available from antique jewellery.Recently, small finds have again been made in Russia, and a small quantity of fine quality stones have recently come onto the market. Gemstone lovers wishing to acquire a piece of demantoid garnet should take this opportunity to do so. If the current seams of demantoid run out, there may be another century without new stocks of demantoid becoming available.
Tsavolite GarnetTsavolite, previously called tsavorite, is a bright green variety of grossular garnet, its colour being induced by the presence of chromium.
Topazolite
A name used for a variety of garnet with a topaz-yellow or an olive green colour.
MagnetismSome types of garnet, particularly the reddish "African" garnets, which are usually found in close association with diamonds, showing distinct magnetism.
A name used for a variety of garnet with a topaz-yellow or an olive green colour.
Magnetism
Some types of garnet, particularly the reddish "African" garnets, which are usually found in close association with diamonds, showing distinct magnetism.
Garnet is a naturally occurring gemstone.Its name comes from Latin granatus meaning seed, because it often resembles small round seeds when found in its matrix rock.Rather than a single gemstone, garnet is a family of related minerals, some of which occur as gemstones.Each has a common crystal structure, and a similar chemical composition.The popular understanding of garnet is as an inexpensive dark red stone. Because it is relatively common and inexpensive, it is often thought of as "only garnet", and as being inferior.This bias extends to other rare and attractive forms of garnet.
Colour
Garnet occurs naturally in a large range of colours including: red, orange, brown, green, yellow, and brown.
Two Families of Garnet
There are two main theoretical groups or "families" of garnet:- pyrope, almandite, spessartite, which are all (metal) aluminium silicates, anduvarovite, grossularite, andradite, which are all calcium (metal) silicates.In practice, there are probably very few garnets with the precise pure chemical composition shown for their type, almost all garnets are of mixed types, where one type is partially replaced by another type.
Trade Terminology
In the trade, gem dealers hardly ever refer to their stock as "pyrope" or "almandite". Instead, they will often refer to "brown" or Indian garnets. As we have stated, very few, if any, pure "types" of garnet occur, most specimens approximate to a particular type.Brown and purpleish "Indian" garnets will usually be towards the pyrope end of the pyrope-almandite axis.Reddish "African" garnets will usually be towards the almandite end of the pyrope-almandite axis.Rhodolite garnets are usually about midway along the pyrope-almandite axis.
Demantoid Garnet
Demantoid garnet is a rare and beautiful bright grass green sub-variety of andradite garnet. It appears to have first been discovered around 1892 in the Bobrovka area of Russia.The Bobrovka is a small tributary of the River Tschussowaja in the Sissersk region on the western side of the Ural Mountains.It was at first thought to be emerald, which is found nearby, and has been erroneously called "Uralian emerald".The name demantoid means diamond-like, because it has a very high adamantine lustre, and a colour dispersion higher than diamond. The only disadvantageous property of demantoid is its low hardness figure at about 6.5 Moh. It is the softest of the garnets, and is more suitable for use in brooches, pendants, or ear-rings, rather than rings, because of this.The brilliant colour of demantoid garnet is due to partial replacement of the silicate by chromic oxide.A diagnostic characteristic of demantoid is the inclusion of radiating fibres of byssolite (asbestos) fibres in a pattern described as a horse-tail. There is no other green stone which shows this feature.In late Victorian times, and early in the twentieth century, demantoid became a very sought after stone. It commanded high prices because it has never been available in large quantity. In recent decades, it has been unobtainable as newly mined stones, and has only been available from antique jewellery.Recently, small finds have again been made in Russia, and a small quantity of fine quality stones have recently come onto the market. Gemstone lovers wishing to acquire a piece of demantoid garnet should take this opportunity to do so. If the current seams of demantoid run out, there may be another century without new stocks of demantoid becoming available.
Tsavolite Garnet
Tsavolite, previously called tsavorite, is a bright green variety of grossular garnet, its colour being induced by the presence of chromium.
Two Families of GarnetThere are two main theoretical groups or "families" of garnet:- pyrope, almandite, spessartite, which are all (metal) aluminium silicates, anduvarovite, grossularite, andradite, which are all calcium (metal) silicates.In practice, there are probably very few garnets with the precise pure chemical composition shown for their type, almost all garnets are of mixed types, where one type is partially replaced by another type.
Trade TerminologyIn the trade, gem dealers hardly ever refer to their stock as "pyrope" or "almandite". Instead, they will often refer to "brown" or Indian garnets. As we have stated, very few, if any, pure "types" of garnet occur, most specimens approximate to a particular type.Brown and purpleish "Indian" garnets will usually be towards the pyrope end of the pyrope-almandite axis.Reddish "African" garnets will usually be towards the almandite end of the pyrope-almandite axis.Rhodolite garnets are usually about midway along the pyrope-almandite axis.
Demantoid GarnetDemantoid garnet is a rare and beautiful bright grass green sub-variety of andradite garnet. It appears to have first been discovered around 1892 in the Bobrovka area of Russia.The Bobrovka is a small tributary of the River Tschussowaja in the Sissersk region on the western side of the Ural Mountains.It was at first thought to be emerald, which is found nearby, and has been erroneously called "Uralian emerald".The name demantoid means diamond-like, because it has a very high adamantine lustre, and a colour dispersion higher than diamond. The only disadvantageous property of demantoid is its low hardness figure at about 6.5 Moh. It is the softest of the garnets, and is more suitable for use in brooches, pendants, or ear-rings, rather than rings, because of this.The brilliant colour of demantoid garnet is due to partial replacement of the silicate by chromic oxide.A diagnostic characteristic of demantoid is the inclusion of radiating fibres of byssolite (asbestos) fibres in a pattern described as a horse-tail. There is no other green stone which shows this feature.In late Victorian times, and early in the twentieth century, demantoid became a very sought after stone. It commanded high prices because it has never been available in large quantity. In recent decades, it has been unobtainable as newly mined stones, and has only been available from antique jewellery.Recently, small finds have again been made in Russia, and a small quantity of fine quality stones have recently come onto the market. Gemstone lovers wishing to acquire a piece of demantoid garnet should take this opportunity to do so. If the current seams of demantoid run out, there may be another century without new stocks of demantoid becoming available.
Tsavolite GarnetTsavolite, previously called tsavorite, is a bright green variety of grossular garnet, its colour being induced by the presence of chromium.
Topazolite
A name used for a variety of garnet with a topaz-yellow or an olive green colour.
MagnetismSome types of garnet, particularly the reddish "African" garnets, which are usually found in close association with diamonds, showing distinct magnetism.
A name used for a variety of garnet with a topaz-yellow or an olive green colour.
Magnetism
Some types of garnet, particularly the reddish "African" garnets, which are usually found in close association with diamonds, showing distinct magnetism.
Fire Opal
Fire Opal
A Variety of OpalFire opal is a variety of opal. It is bright orange in colour, and always reminds us of barley sugar sweets. It can vary from completely translucent without any opalescence or iridescence, to semi-translucent with very noticeable flashes of iridescent colour.It is often called Mexican fire opal, because Mexico is one of its prime sources.
Aztec Gold
Fire opal was known to the Aztecs between about 1200 to 1519 AD.
A Variety of OpalFire opal is a variety of opal. It is bright orange in colour, and always reminds us of barley sugar sweets. It can vary from completely translucent without any opalescence or iridescence, to semi-translucent with very noticeable flashes of iridescent colour.It is often called Mexican fire opal, because Mexico is one of its prime sources.
Aztec Gold
Fire opal was known to the Aztecs between about 1200 to 1519 AD.
Emerald
Emerald
Emerald is the grass green variety of the gemstone called beryl. Although all emeralds are beryl, not all beryls are emerald.
Colouration
Pure beryl is colourless, often called white, and although quite rare, tends not to be valuable because it does not have much brilliance. Colours, as in many gemstones, are caused by small amounts of impurity, usually metallic oxides. This is a another case where impurity is desirable.Chromium, in the form of chromic oxide, causes the bright grassy green colouring in beryl, thereby producing emeralds.Vanadium can also affect the exact shade, as may traces of iron.It is also possible to have green beryl which is not emerald, because the colouring agent is not chromium.
Hardness
Emerald, along with other beryls, is quite hard, having a hardness of 71/2 to 8 on Moh's scale, compared with 10 for diamond, 9 for corundum, and 8 for topaz. Hardness is generally a desirable feature is gemstones.
Sources
The earliest known source of emerald was near the Red Sea in Egypt, the so-called Cleopatra's emerald mines. They were probably worked from about 2000 B.C., apparently the location of them was lost in the middle ages, and not rediscovered until 1818. Most emeralds used in ancient jewellery are believed to have come from these mines. They are not worked nowadays because of the low quality of crystals found.Emeralds have been found in Austria since Roman times, in the Legbach ravine at Habachtal near Salzburg. These are no longer commercially mined.Columbia is generally recognised as the source of the world's finest quality emeralds, both in the past and the present. The Columbian Indians were using them before 1537, when Quesada conquered Columbia. Later the Spanish discovered that the emerald mines were at Somondoco, which means "god of the green stones", and which is now known as Chivor. The best coloured Columbian emeralds are said to be those from the Muzo mine, although another mine at Cosquez is also highly rated.Russia has been another important source of emeralds in the past. Most Russian emeralds coming from Sverdlovsk or Ekaterinburg in the Ural Mountains.Emeralds were discovered in Australia in 1890 in New South Wales.Emeralds were discovered between1927 and 1929 at Gravelotte in South Africa, followed by other sources.Another important source of superb quality emeralds, usually only of small size, is Sandawana in Zimbabwe formerly Southern Rhodesia. These were discovered only in 1956.Emeralds were known in India from antiquity, but their source is not certain. The earliest known Indian source was 1929 at Arawalli in Rajahstan, other sources being discovered since. The quality of Indian emeralds is very variable, but most are of lower quality which are often polished as beads.Other sources of emerald include Norway, North Carolina, Connecticut, Maine, New Hampshire, although non of these are very important.
Emerald is the grass green variety of the gemstone called beryl. Although all emeralds are beryl, not all beryls are emerald.
Colouration
Pure beryl is colourless, often called white, and although quite rare, tends not to be valuable because it does not have much brilliance. Colours, as in many gemstones, are caused by small amounts of impurity, usually metallic oxides. This is a another case where impurity is desirable.Chromium, in the form of chromic oxide, causes the bright grassy green colouring in beryl, thereby producing emeralds.Vanadium can also affect the exact shade, as may traces of iron.It is also possible to have green beryl which is not emerald, because the colouring agent is not chromium.
Hardness
Emerald, along with other beryls, is quite hard, having a hardness of 71/2 to 8 on Moh's scale, compared with 10 for diamond, 9 for corundum, and 8 for topaz. Hardness is generally a desirable feature is gemstones.
Sources
The earliest known source of emerald was near the Red Sea in Egypt, the so-called Cleopatra's emerald mines. They were probably worked from about 2000 B.C., apparently the location of them was lost in the middle ages, and not rediscovered until 1818. Most emeralds used in ancient jewellery are believed to have come from these mines. They are not worked nowadays because of the low quality of crystals found.Emeralds have been found in Austria since Roman times, in the Legbach ravine at Habachtal near Salzburg. These are no longer commercially mined.Columbia is generally recognised as the source of the world's finest quality emeralds, both in the past and the present. The Columbian Indians were using them before 1537, when Quesada conquered Columbia. Later the Spanish discovered that the emerald mines were at Somondoco, which means "god of the green stones", and which is now known as Chivor. The best coloured Columbian emeralds are said to be those from the Muzo mine, although another mine at Cosquez is also highly rated.Russia has been another important source of emeralds in the past. Most Russian emeralds coming from Sverdlovsk or Ekaterinburg in the Ural Mountains.Emeralds were discovered in Australia in 1890 in New South Wales.Emeralds were discovered between1927 and 1929 at Gravelotte in South Africa, followed by other sources.Another important source of superb quality emeralds, usually only of small size, is Sandawana in Zimbabwe formerly Southern Rhodesia. These were discovered only in 1956.Emeralds were known in India from antiquity, but their source is not certain. The earliest known Indian source was 1929 at Arawalli in Rajahstan, other sources being discovered since. The quality of Indian emeralds is very variable, but most are of lower quality which are often polished as beads.Other sources of emerald include Norway, North Carolina, Connecticut, Maine, New Hampshire, although non of these are very important.
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