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A gemstone or gem, also called a precious or semi-precious stone, is a piece of attractive mineral, when cut and polished, is used to make jewellery or other adornments. However certain rocks, (such as lapis-lazuli) and organic materials (such as amber or jet) are not minerals, but are still used for jewellery, and are therefore often considered to be gemstones as well.
Most gemstones are hard, but some soft minerals are used in jewellery because of their lustre or other physical properties that have aesthetic value. Rarity is another characteristic that lends value to a gemstone.
A gemstone is treasured for its beauty, so appearance is nearly always its most important attribute. Characteristics that make a stone beautiful or desirable are colour, unusual optical phenomena within the stone, such as iridescence, interesting inclusions and rarity. Not all of these characteristics have to be present to make a stone highly desirable – diamond, for example, is prized because it is the hardest naturally occurring substance known and is able to reflect light brilliantly. Diamonds are far from rare, however, with millions of carats mined each year.
Opaque and translucent stones, such as opal and turquoise are commonly cut as cabochons, to show off their colour and surface properties.
Transparent gems are normally faceted, a method which shows the optical properties of the stone’s interior to its best advantage by maximising reflected light and thus making the stone ‘sparkle’ more. The facets must be cut at the right angles to optimize the light reflected back to the viewer, and this depends on the optical properties of the gem. Special equipment is used to hold the stone onto a flat lap for cutting and polishing the flat facets.
Treatment of Gemstones
Heat Treatment
Gemstones are often treated by heat, either to improve colour or clarity, or sometimes even to change the classification of the stone – mostly citrine, for example, is made by heating amethyst. Aquamarine is often heat-treated to remove yellow tones and give a purer blue and nearly all tanzanite is heated to remove brown undertones and give a more desirable blue/purple colour. A significant majority of sapphire and ruby is treated with high heat to improve both colour and clarity.
Waxing / Oiling
This is done most commonly with emerald, to fill and disguise the natural fissures that each stone contains. The wax or oil is also often coloured to improve the colour of the stone as well as its clarity. Turquoise is also often similarly treated.
Radiation
This is not a very common treatment. However, it is used in some gemstones - most blue topaz acquires its colour by being irradiated to change the colour from white to blue.
Coatings
Recently, a technique has become available whereby a gemstone can be enhanced with a coating that changes the color and appearance of the gem. Topaz, for example, is sometimes treated with a layer of titanium dioxide that changes its colour to a more golden hue with some apparent iridescence. This coating is not permanent and can be damaged by scratching.
Synthetic and artificial gemstone
Some gemstones are manufactured to imitate other gemstones. The imitations copy the look and colour of the real stone but possess neither their chemical nor physical characteristics and tend not to have the durability or long-lasting attractiveness. However, it is vital to differentiate between imitation gemstones and those that have been synthetically produced but are still ‘real’. Diamonds, ruby, sapphires and emeralds which possess very nearly identical chemical and physical characteristics to the genuine article have been manufactured in labs, for example. Synthetic corundums, including ruby and sapphire, are very common and cost only a fraction of the natural stones. There is without a doubt something about the history and age of a ‘genuine’, naturally occurring gemstone, however, that cannot be replaced by the synthetic manufactured variety.
You can learn more about each gemstone with our comprehensive guide.
Agate
Alexandrite
Amber
Amethyst
Andalusite
Apatite
Aquamarine
Beryl
Carnelian
Chalcedony
Chrysoberyl
Chrysoprase
Citrine
Coral
Corundum
Demantoid garnet
Diamond
Emerald
Feldspar
Fire Opal
Garnet
Hematite
Iolite
Jade
Jet
Labradorite
Lapis Lazuli
Larimar
Moonstone
Mother of Pearl
Onyx
Opal
Pearl
Peridot
Pyrope Garnet
Quartz
Rhodolite Garnet
Rock Crystal
Ruby
Sapphire
Spessartite Garnet
Spinel
Tahitian Pearl
Tanzanite
Topaz
Tourmaline
Turquoise
Tzavorite Garnet
Agate is the name given to a wide selection of varieties of chalcedony, a form of quartz. Many agates are naturally coloured, while others are stained to give a stronger decorative effect.
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Agate is formed by filling a cavity in a host rock and as a result, agate is often found in the form of rounded nodules or geodes, with concentric bands like the ring of a tree trunk. These bands can create stunning, picturesque effects and because this is so variable, different types of agate have been given many different descriptive names. Moss agate, for example, has a plant-like pattern on its surface.
When split or sliced, these geodes show their banding to brilliant effect. In some geodes there is a central cavity, while in others the centre is hollow – as a result, the Indians of the western American states called agate nodules "thunder eggs".
Agate can be found in many different colours, from grey through green to rich dark red tones. Agate sometimes contains organic material which has been fossilized – over time the organic material is replaced so that its shape remains. Fossilised or petrified wood is an unusual and attractive form of agate.
Agate was highly valued as a talisman in ancient times and is held to have considerable powers in many traditions – it is believed to cure the stings of scorpions and the bites of snakes, soothe the mind, prevent contagion, quench thirst and still thunder and lightning. Persian magi are known to have prized agate rings, using them, amongst other things to divert storms.
An extensive collection of three thousand agate bowls amassed by Mithridates, king of Pontus, demonstrates the popularity of agate and the agate bowls found in European museums, including the Louvre, show the enthusiasm with which they were collected by European royalty during the Renaissance.
ALEXANDRITE
Alexandrite is a rare gemstone. The very first Alexandrite crystals were discovered in the emerald mines near the Tokovaya River in the Urals in 1834. This discovery was made on the day the future tsar of Russia, Alexander II (1818 – 1881) came of age. So, this gemstone was consequently named after him.
Alexandrite is a vivid green colour by natural daylight, but typically appears purple-red in artificial light. Alexandrite became the national stone of tsarist Russia as the stone shows both red and green, the principal colours of old Imperial Russia.
This stone became hugely popular with Russian jewellery designers and it now can be found in antique Russian jewellery. It was also occasionally used in some Victorian jewellery in England. In modern fine jewellery, however, it is seldom used despite its beauty simply because it is so exceptionally rare.
Since the stones from the Urals became available on the market, Russia has remained the primary source of alexandrite. In 1987, Alexandrite was discovered in Brazil which had distinctive colour, pleochroism and clarity. Today Hematita in Brazil is one of the most important alexandrite deposits. Occasionally, alexandrite displaying chatoyancy (the cat’s eye phenomenon observed in chrysoberyl) is found there, which was never seen among the alexandrites in Russia. Alexandrite has since also been found in Sri Lanka, India, Burma, Madagascar and Zimbabwe.
Finely cut and faceted alexandrites above one carat are among the most expensive gemstones in the world, even more so than fine ruby, sapphire or emerald.
AMBER
Amber is fossil tree resin, which is appreciated for its color and beauty. Although not mineralised, it is often classified as a gemstone.
Most of the world's amber is in the range of 30–90 million years old. Because it used to be soft and sticky tree resin, amber can sometimes contain insects and even small vertebrates.
Semi-fossilized resin or sub-fossil amber is known as copal.
Amber occurs in a range of different colors. As well as the usual yellow-orange that is associated with the color "amber", amber itself can range from a whitish color through a pale lemon yellow, to brown and almost black. Other more uncommon colors include red amber (sometimes known as "cherry amber"), green amber, and even blue amber, which is rare and highly sought after.
A lot of the most highly-prized amber is transparent, but cloudy amber and opaque amber is also very common.
Amber is quite light and warm to the touch, and readily produces static electricity when rubbed. In fact, it was known to the ancient Greeks as elektron, from which we coined the word electricity. The metal electrum was also named after it, being similar in colour to amber.
Heating amber will soften it and eventually it will burn, which is why in Germanic languages the word for amber is a literal translation of burn-Stone.
In the Middle Ages in Germany, amber was used for burning as an aromatic incense.
Treatment of amber
Amber is treated largely to increase its clarity. Heating amber in rape seed oil penetrates the air spaces and increases the clarity. This can result in sun spangles developing – far from being an unwanted side effect, however, these inclusions are an attractive end-product and are often produced deliberately.
Fossilised Insects
The resin contains, in addition to the beautifully preserved plant-structures, remains of insects, spiders, annelids, frogs, crustaceans and other small organisms which were trapped by the sticky surface and became enveloped while the exudation was fluid.
Since the book and movie Jurassic Park, Dominican Amber has become world famous. Dominican amber differentiates itself from Baltic Amber by being mostly transparent and often containing a higher number of fossil inclusions.
Amber in Jewellery
Amber was among the first stones used as human adornment. It is occasionally faceted, but is usually cut or polished as cabochon or as beads, to emphasise the warmth of its colour and smoothness of surface. Its light weight makes it ideal for use as large stones in rings, pendants, bracelets and earrings and is often set in silver.
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Sources
Amber deposits are found around the world. Some are much older than the well known amber deposits in the Baltic countries and the Dominican Republic, others are much younger. A lesser known source of amber is in the Ukraine, within a marshy forested area on the Volyhn-Polesie border.
AMETHYST
Amethyst is a violet variety of quartz mostly used as an ornamental stone in jewellery. The name comes from the Ancient Greek a- ("not") and methustos ("intoxicated"), a reference to the belief that the stone protected its owner from drunkenness; the ancient Greeks and Romans wore amethyst and made drinking vessels of it in the belief that it would prevent intoxication.
Because it has a hardness of seven on the Mohs scale, amethyst is suitable for use in jewellery.
Amethyst occurs in primary hues from a light slightly-pinkish violet to a deep grape purple. Amethyst may exhibit one or both secondary hues, red and/or blue.
Amethyst is produced in abundance from the state of Minas Gerais in Brazil where it occurs in large geodes within volcanic rocks. It is also found and mined in South Korea, Austria, Uruguay, Russia, India, and Zamibia.
AQUAMARINE
Aquamarine (Lat. aqua marinā, "water of the sea") is a gemstone-quality transparent variety of beryl, having a delicate blue or turquoise color, suggestive of the tint of seawater. It is closely related to the gem emerald. Colours vary and yellow beryl (heliodor), rose pink beryl (morganite), and white beryl (goshenite) are known.
Aquamarine has a Mohs hardness of 7.5 to 8.
Some of the finest varities of Aquamarine come from Russia, Brazil, Sri Lanka.
In the United States, aquamarines can be found at the summit of Mt. Antero in central Colorado. Aquamarine is the official state gem of Colorado and Missouri.
Aquamarine (along with bloodstone) is the birthstone associated with March.
It is also the gemstone for the 19th Anniversary.
CARNELIAN
Carnelian, sometimes spelled cornelian, is a red or reddish-brown variant of chalcedony.
Carnelian was used widely during Roman times 2,000 years before the present era to make signet or seal rings for imprinting a seal with wax on correspondence or other important documents.
The word carnelian is derived from the Latin word caro, carnis meaning flesh, in reference to the flesh color sometimes exhibited. Its red colour is due to the presence of iron impurities in its structure. It can vary from a pale, fleshy pink through a brownish orange colour to a clear red.
The mineral is found worldwide, but India is reputed for developing the best gemstones.
CHALCEDONY
Chalcedony is a silica mineral having a waxy lustre, 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.
The more notable varieties of chalcedony are:
Agate, Carnelian, Chrysoprase, Heliotrope, and Moss agate.
Chalcedony was one of the earliest raw materials used by mankind. As early as the Bronze Age chalcedony was in use in the Mediterranean region. The earliest recorded use of chalcedony was for knives, tools and containers such as cups and bowls, decorative articles, and jewellery.
The Native Americans used chalcedony as a sacred stone that could promote stability within the ceremonial activities of the tribe. Hot wax would not stick to it so it was often used to make seal impressions.
Chalcedony is said to augment emotional balance and vitality and to alleviate hostility.
CITRINE
Citrine is a variety of quartz. It ranges in colour from a pale yellow to brown. The name is derived from the colour - the yellow of the lemon.
Citrine has ferric (iron-containing) impurities, and is rarely found naturally. Most commercial citrine is in fact artificially heated amethyst or smoky quartz.
Brazil is the leading producer of citrine, with much of its production coming from the state of Rio Grande do Sol.
In the past, citrine was carried as a protection against snake venom and evil thoughts.
Citrine is one of three traditional birthstones for the month of November.
CORAL
Coral is an organic gemstone, and hence is similar to Pearl in this respect. It grows in warm seas, such as the Mediterranean Sea, Southern Seas and the Pacific ocean, and is effectively the calcium carbonate ‘skeleton’ of individual polyps (plant-like animals) that form the beautiful underwater colonies.
Coral is given its shine by polishing, and is usually made into cabochon or into beads, but can also be carved. Coral is most commonly found in red and pink, but it can also be black, white, brown, gold and even blue.
Coral is collected by hand by specially trained divers. It is then cleaned, sorted, cut and prepared for use in jewellery.
Indians believe that coral wards off negative powers, and coral powder and ash is used in making Ayurvedic medicine. It is also used to carve statuettes and prayer beads in Tibet, as coral is believed to be auspicious.
There is also evidence that the Greeks and Romans used this stone to adorn rings, caskets and tiaras, and that merchants and sailors in the past used to carry fragments of coral as a talisman against witches. It was also used for medicinal purposes, with its powder being added to, amongst other things, the food of babies and young children to protect them from epidemics.
GARNET
Garnet is a group of minerals that have been used since the Bronze Age as gemstones and abrasives. Garnets are most often seen in red, but are available in a wide variety of colors spanning the entire spectrum. The name "garnet" comes from the Latin granatus (" grain"), possibly a reference to the Punica granatum ("pomegranate"), a plant with red seeds similar in shape, size, and color to some garnet crystals.
The rarest of the garnets is the blue garnet, discovered in the late 1990s in Bekily, Madagascar. It is also found in parts of the United States,Russia and Turkey. It changes color from blue-green in the daylight to purple in incandescent light, as a result of the relatively high amounts of vanadium. Other varieties of colour-changing garnets exist. In daylight, their color ranges from shades of green, beige, brown, gray, and blue, but in incandescent light, they appear a reddish or purplish/pink color. Because of their color changing quality, this kind of garnet is often mistaken for Alexandrite.
Garnet species’s light transmission properties can range from the gemstone-quality transparent specimens to the opaque varieties used for industrial purposes as abrasives.
Its hardness on the Mohs Scale is about 6.5 to 7.5.
- In the USA it is known as the birthstone for January.
- It is the gemstone for the 2nd wedding anniversary.
- It is also New York’s gemstone.
IOLITE
The name "iolite" comes from the Greek word for violet. Another old name is dichroite, a Greek word meaning "two-colored rock", a reference to cordierite's strong pleochroism. It has also been called "water-sapphire" and "Vikings' Compass" (because of it's ability to determine the direction of the sun on overcast days).
Gem quality iolite varies in color from sapphire blue to blue violet to yellowish gray to light blue as the light angle changes.
Iolite is found in Sri Lanka, India, Burma, Australia's Northern Territory, Namibia, Brazil, Tanzania, Madagascar, Connecticut, and the Yellowknife area of the Northwest Territories of Canada.
JADE
The term jade is applied to two different rocks that are made up of different silicate minerals. Nephrite jade consists of the calcium- and magnesium-rich mineral actinolite. Jadeite, the second form of jade consists of a sodium- and aluminium-rich pyroxene. The trade name Jadite is sometimes applied to translucent/opaque green glass.
The English word 'jade' is derived from the Spanish term piedra de ijada (first recorded in 1565) or 'loin stone', from its reputed efficacy in curing ailments of the loins and kidneys.
Nephrite and jadeite were used by people from the prehistoric for similar purposes. Both are about the same hardness as quartz, and they are exceptionally tough. They are beautifully coloured and can be delicately shaped..
Among the earliest known jade artifacts excavated from prehistoric sites are simple ornaments with bead, button, and tubular shapes. Additionally, jade was used for axe heads, knives, and other weapons. As metal-working technologies became available, the beauty of jade made it valuable for ornaments and decorative objects.
Jade has a Mohs hardness of between 6.5 and 7.0.
LABRADORITE
Labradorite is a gem variety of feldspar mineral. It is a particularly beautiful gemstone because of its light-scattering property (also known, because of its occurrence in labradorite, as labradorescence), which is a glowing iridescent colour display inside the stone, often colloquially referred to as ‘fire’. This is caused by interference effects of light due to the fine layers in the structure of the stone.
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Labradorite is usually grey, with green and blue schiller. Yellow, gold, red and purple are also displayed when the stone is viewed from different angles.
Labradorite is named after the Labrador Peninsula in Canada where it was first discovered in 1770. It is also found in Canada and some of the Scandinavian regions.
The Native Indians of Labrador attributed mystical qualities to labradorite, calling it ‘firestone’ because of its magnificent display of colour. Powdered labradorite was often used to cure their ailments.
LAPIS LAZULI
Lapis lazuli is prized since antiquity for its intense blue colour. Lapis lazuli is a rock, not a mineral: whereas a mineral has only one constituent, lapis lazuli is formed from more than one mineral.
The best lapis lazuli is found in limestone in the Kokcha river valley of Badakhshan province in northeastern Afghanistan. Badakhshan was the source of lapis for the ancient Egyptian and Mesopotamian civilizations, as well as the later Greek and Roman; during the height of the Indus valley civilisation about 2000 B.C. Other sources include Chile, the Lake Baikal region of Russia, Siberia, Angola, Burma, India, Pakistan USA (Colorado and California), and Canada.
In ancient Egypt lapis lazuli was a favorite stone for amulets and ornaments. It was also used by the Assyrians and Babylonians for seals. Lapis jewellery has been found at excavations of the Predynastic Egyptian site Naqada (3300–3100 B.C.), and powdered lapis was used as eyeshadow by Cleopatra.
LARIMAR
Larimar is an extremely rare gemstone that has been found in only one location, in a mountainous, relatively inaccessible region of the Dominican Republic overlooking the Caribbean Sea. Most larimar jewellery are prooduced is set in silver but high grade stones are often set in gold.
Discovered in 1974 by Norman Rilling, a member of the Peace Corps of the United States, and Miguel Méndez, a Dominican found on the seashore. larimar has an extraordinary blue appearance similar to the colour of the ocean in tropical areas. The name ‘Larimar’ was given by the Dominican who discovered the stone. It is a combination of Larissa (his daughter's name) and Mar, the Spanish word for sea.
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MOONSTONE
Moonstone is the best known gem variety of feldspar mineral. It is usually polished as a cabochon. Its importance as a gemstone arises because of its schiller, which is an iridescent colour-display effect also found in labradorite.
A classic moonstone is usually almost transparent with warm blue, purple and greenish schiller. Its body colour can, however, also be found in pink, green, brown and blue.
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Inclusions occurring in moonstone often make interesting patterns and can generally add to the attractiveness of the stone.
Moonstone was particularly popular about a century ago at the time of the Art Nouveau wave. It is particularly noticeable in designer jewellery by the French master goldsmith Rene Lalique and his contemporaries, which can be found in museums around the world today.
In India, moonstones are thought to bring the wearer beautiful dreams, and are consequently known as ‘dream stones’. In many places in the Middle East, the moonstone is considered a symbol of fertility and women wear them sewn out of sight in their garments.
Traditionally, classical moonstones come from Sri Lanka. However, they are also found in the USA, Brazil, Australia, Myanmar and Madagascar. Since bluish moonstones of good quality have been becoming more and more of a rarity in recent years, their prices have risen sharply.
There are also several unusual varieties of moonstone, some with a smokey colour, some the colour of champagne, and some black and some reddish ones, mainly originating from India.
Mother of pearl is the common name for iridescent nacre, a blend of minerals that are secreted by oysters and other mollusks and deposited inside their shells, coating and protecting their bodies from parasites and foreign objects.
Nacre is the substance that is deposited around an object that becomes lodged in the mollusk either naturally or inserted by humans -to become a pearl. Nacre is strong, resilient, and iridescent.
Although pearls are popular today, some past cultures regarded colorful pieces of mother of pearl as more desirable decoration for jewelry and other objects.
Jewelry made from mother of pearl is in the group called organic jewellery, which includes all jewellery that originates from a living creature, plant or other living organism.
Chief sources are the pearl oyster, found in warm and tropical seas, primarily in Asia; freshwater pearls mussels, which live in many rivers of the United States, Europe, and Asia; and the abalone of California, Japan, and other Pacific regions.
ONYX
Onyx is a banded form of quartz. The colors of its bands range from white to almost every color (save some shades, such as purple or blue). Pure black Onyx is common, and perhaps the most famous variety, but not as common as Onyx with banded colors.
It is usually cut as a cabochon, or into beads, and is also used for intaglios and cameos, where the bands make the image contrast with the ground. Some onyx is natural but much is produced by the staining of agate.
Black onyx is an especially effective backdrop for coloured stones, particularly opaque ones such as coral and jade, and as such is particularly popular in designer jewellery. Due to its fine texture, it is also ideal for carving, making it a popular material for today's lapidary artists. Onyx is also often used in fine jewellery to contrast with carved rock crystal and the deep colours of rubies, sapphires, and emeralds.
The principal source of onyx is Brazil, but it is also available from parts of the USA, Germany, Mexico, India, and Africa.
OPAL
The word opal comes from the Latin opalus, by Greek opallios, and is from the same root as Sanskrit upálá[s] for "stone", originally a millstone with upárá[s] for slab. Precious opal shows a variable interplay of internal colors The term opalescence is commonly and erroneously used to describe this unique and beautiful phenomenon, which is correctly termed play of colour.
Opal is found in many varieties:
Fire opal – Fire opals are transparent to translucent opals with warm body colors yellow, orange, orange-yellow or red and they do not show any play-of-color. The most famous source of fire opals is the state of Queretaro in Mexico and these opals are commonly called Mexican fire opals.
Peruvian opal (also called blue opal) is a semi-opaque to opaque blue-green stone found in Peru which is often cut to include the matrix in the more opaque stones. It does not display pleochroism.
Common opal
Besides the gemstone varieties that show a play of colour, there are other kinds of common opal: - Milk opal, milky bluish to greenish (which can sometimes be of gemstone quality).
- Resin opal, honey-yellow with a resinous luster.
- Wood opal, caused by the replacement of the organic material in wood with opal.
- Menilite, brown or grey opal.
- Hyalite, a colourless glass-clear opal sometimes called Muller's Glass.
- Geyserite deposited around hot springs or geysers.
- Diatomite or diatomaceous earth, the accumulations of diatom shells or tests.
Australia produces around 97% of the world’s opal. Another source of white base opal in the United States is Spencer, Idaho. Other significant deposits of precious opal around the world can be found in the Czech Republic, Slovakia, Hungary, Turkey, Indonesia, Brazil, Honduras, Guatemala, Nicaragua and Ethiopia.
Opals are also Australia’s national gemstone.
Opal is the traditional birthstone of the month of October.
PEARL
A pearl is a hard, roundish object produced within the soft tissue of a living shelled mollusk. Just like the shell of mollusks, a pearl is composed of calcium carbonate in minute crystalline form, which has been deposited in concentric layers.
A nacreous pearl is made from layers of nacre, by the same living process as is used in the secretion of the mother of pearl which lines the shell. A "natural pearl" is one that formed without any human intervention at all, in the wild, and is very rare. A "cultured pearl", on the other hand, is one that has been formed on a pearl farm. The great majority of pearls on the market are cultured pearls.
There are several types of pearls known for their distinct beauty, including South Sea Cultured Pearls, Tahitian Pearls, and Keshi Pearls.
South Sea pearls are among the largest cultured pearls in the world. The South Seas are between the northern coast of Australia and the southern coast of China. South Sea pearls are usually monitored and grown for 2 years before they are harvested. This explains the size of these pearls.
An average South Sea pearl measures 13mm, and most harvests produce a range of sizes between 9mm and 20mm. The nacre of South Sea pearls is unusually thick, and because it is particularly rapidly deposited from warm waters, has a uniquely satiny lustre. As well as white, South Sea pearls can also be found in a variety of colours that are unusual in other types, such as silver and gold.
Black Tahitian pearls are produced by the black-lipped oyster in the islands of French Polynesia. Tahitian pearls are often large in size, due to the considerable size of the oyster. The natural dark colours of the pearls make them unique. Tahitian pearls are a variety of shades – gray, silver, charcoal and so on. Truly black pearls are very rare and desirable.
Keshi pearls are formed by the oyster rejecting and spitting out the implanted irritant before the culturing process is complete. Because they have no nucleus, keshi pearls vary widely in shape and colour and, being 100% nacre, are especially lustrous and shiny. This makes them an especially beautiful gem to be used in handmade and designer jewellery. In fact, most keshi have greater lustre than even the best-quality cultured pearls. They can form in either saltwater or freshwater and are generally quite small in size.
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PERIDOT
Peridot (a type of olivine stone) is one of the few gemstones that occur in only one color: basically an olive green. The intensity and tint of the green however depends on how much iron is contained in the crystal structure, so the color of individual peridot gems can vary from yellow-green through olive green to brownish green.
Peridot crystals have been collected from some Pallasite meteorites. Peridot is often found in lavas and in peridotite xenoliths of the earths’s mantle which lavas carry to the surface; but gem quality peridot only occurs in a fraction of these settings.
Peridot is mined in North Caroline, Arizona, Hawaii, Nevada, and New Mexico, in the US; and in Australia, China, Brazil, Kenya, Mexico, Burma, Norway, Pakistan, South Africa, Sri Lanka, and Tanzania. High quality peridot olivine is mined in the eastern lava fields of Saudi Arabia.
Peridot is the birthstone for August.
QUARTZ
Quartz is essentially a crystalline rock composed of silicon dioxide. It is very common, being the most abundant single mineral on earth. It makes up about 12% of the earth’s crust, occurring in a large variety of igneous, metamorphic and sedimentary rocks. There are innumerable varieties of quartz, a number of which are gemstones; however, some of these varieties are very rare.
Common quartz is usually colourless or white, and its crystals are transparent to translucent.
Many gemstones including Chalcedony, Tiger Eye, Agate, Carnelian, Onyx, Jasper, Aventurine, Rock crystal are varieties of quartz. Other varieties of quartz include Amethyst, which is purple, Citrine, which is yellow, Rose quartz which is pink and Smoky quartz, which is transparent to opaqe brown.
As can be seen from this list, the characteristics of quartz are almost infinite – it comes in nearly every colour of the spectrum, some stones are banded, some are nearly opaque, others transparent.
ROCK CRYSTAL
Rock crystal is the name given to all clear colorless quartz. Rock crystal often has inclusions of other minerals and these inclusions sometimes produce popular varieties of ornamental stone. Golden rutile inclusions produce a unique stone aptly named rutilated quartz that has a very hair-like look. Another apply named stone is called tourmalinated quartz and contains intricatly crossing needles of black schorl tourmaline trapped in the clear crystal.
Its name is derived from the Greek word krustallos meaning ice, because the Greeks, finding it in caves near Mount Olympus, believed it to be water which had been permanently frozen by the gods.
The finest rock crystal is from the Hot Springs area of Arkansas. It is also sourced in Cumberland, Switzerland, Brazil and Madagascar. Some of the largest individual crystals of quartz have been found in Brazil, weighing over 44 tonnes.
RUBY
A ruby is a pink to blood red gemstone, a variety of the mineral corundrum (aluminium oxide). The common red color is caused mainly by the element chromium. Its name comes from ruber, Latin for red. Other varieties of gem-quality corundum are called sapphires. It is considered one of the four precious stones, together with the sapphire,the emerald, and the diamond.
Prices of rubies are primarily determined by colour. The brightest and best "red" called pigeon blood red, commands a huge premium over other rubies of similar quality. After colour follows clarity: similar to diamonds, a clear stone will command a premium, but a ruby without any needle-like rutile inclusions will indicate the stone has been treated one way or another. Cut and carat (size) also determine the price.
Rubies are mined in Myanmar (Burma), Thailand, Sri Lanka, Tanzania, Kenya, Madagascar, Vietnam, Cambodia.Rubies are also found in the United States in Montana, North Carolina, and South Carolina. The Mogok Valley in Upper Myanmar has produced some of the finest rubies.
- Ruby is associated with the sun in Vedic astrology.
- Ruby is associated with a 40th wedding anniversary.
- Rubies have always been held in high esteem in Asian countries. They were used to ornament armor, scabbards, and harnesses of noblemen in India and China. Rubies were laid beneath the foundation of buildings to secure good fortune to the structure.
SAPPHIRE
Sapphire refers to gem varieties of the mineral corundrum, an aluminium oxide, when it is a colour other than red. Trace amounts of other elements such as iron, titanium and chromium give corundum their blue, yellow, pink, purple, orange or greenish color.
The word sapphire comes from sapphirus meaning blue, but sapphire can also be red, and, in the type known as ‘fancy sapphires’, a variety of other colours as well.
Some sapphires display pleochroism and change colour from shades of blue in outdoor light to shades of purple in indoor light.
Famous sapphires include the Prince Albert Brooch, a huge sapphire which was given to Queen Victoria by Prince Albert the day before their wedding. The engagement ring given to Elizabeth Taylor by one of her husbands, Michael Wilding, has a huge cabochon sapphire mounted on it. Joan Crawford also received a sapphire engagement ring from her second husband, of 70 carats. She was a great fan of sapphires, to the extent that the press called them ‘Joan Blue’ after her. One of her favourite pieces in her extensive collection included a bracelet set with three star sapphires of 60 carats each. Star sapphires are half-dome-cut sapphires with a starlike effect which seems to glide across the surface of the stone, the way the sliver does in a cat’s eye.
Sapphires are found in India, Burma, Thailand, Vietnam, Australia, Brazil and Africa.
Cutting sapphires is notoriously difficult, because as well as being hard, the stone must be cut in such as way as to maximize the intensity and solidity of the colour of the stone. Once this is achieved, however, sapphire makes one of the most sought-after and attractive gemstones in fine and designer jewellery.
Tanzanite is quite a ‘new’ stone. It is the blue/purple variety of the mineral zoisite which was discovered in the Meralani Hills of Northern Tanzania in 1967, near the city of Arusha. Tanzanite crystals have been growing for millions of years in deposits on the inside of metamorphic hills on a vast plain in the shadow of Kilimanjaro. They were noticed one day by a group of Masai shepherds who noticed the sparkling crystals lying in the sun. They were introduced to the jewellery world in 1969 by Tiffany and Co., who named them after their discovery location to add to their exotic appeal.
Tanzanite is noted for its remarkably strong trichroism, appearing alternately sapphire blue, violet, and burgundy depending on crystal orientation. Tanzanite in its rough state is usually a reddish brown color. And as such is heated to 600 °C in a gemological oven to bring out the classic blue violet of the stone.
The Masai believe that Tanzanite is the stone of birth because of its blue colour, and they give tanzanite to their wives at the birth of their first-born children.
One of the largest refined specimens of tanzanite, named ‘The Midnight Blue’, is 122.7 carats and is located at the Natural History Museum in Washington DC.
Topaz is a silicate mineral of aluminium and fluorine and is best known as a Madeira or sherry-coloured stone. Topaz can also be colourless, blue, green and pink.
The name is believed to be derived from the Greek word topazos, meaning ‘to seek’. This was the ancient name for St John’s Island in the Red Sea, because the island was notoriously difficult to get to. The island is thought to be one of the first places where topaz was discovered. Alternatively, the etymology might be from the Sanskrit word tapas, meaning ‘fire’, to describe its colour.
Topaz has been used and prized for at least 2000 years. It is one of the gemstones which form the foundations of the twelve gates to the Holy City of the New Jerusalem. These so-called apocalyptic stones are intended to serve in protection against enemies and as a symbol of beauty and splendour.
The magnificence of topaz should not be underestimated – it has, on occasion, been mistaken for diamond. The enormous 1680-carat topaz from the Portuguese crown, the Braganza, for example, was for a long time mistaken for diamond.
Topaz can be found in Ahghanistan, Sri Lanka, Czech Republic, Germany, Norway, Pakistan, Mexico, Italy, Sweden, Japan, Brazil, and the United States.
It is the birthstone of the month of November.
Tourmaline is usually thought of as and most commonly found in green, but in fact exists in more colours than any other gemstone, including blue, red, pink, orange, yellow, colourless, brown, purple and black. Pink tourmaline is sometimes referred to as rubellite.
Some tourmalines display pleochroism (more than one colour in the same stone). Indeed, the word tourmaline is thought to derive from the Singhalese words tura mali. Loosely translated, this means something like 'stone with mixed colours'. This refers to the spectacular colour spectrum displayed in this gemstone.
According to an old Egyptian legend, the wide variety of colours is because the tourmaline, on its way up from the centre of the Earth, passed over a rainbow and in doing so assumed all its colours. It also explains, perhaps, why tourmaline is sometimes referred to as the ‘gemstone of the rainbow’ in some cultures.
Tourmalines are often cut as long baguettes, in emerald cuts, or ovals. Relatively speaking, large pieces of tourmalines are more common than in other gemstones, so they are ideal for large handmade jewellery pieces and designer jewellery.
Gem and specimen tourmaline is mined chiefly in Brazil and Africa, and Sri lanka. In addition to these places, tourmaline is mined in Tanzania, Nigeria, Kenya, Madagascar, Mozambique, Namibia, Afghanistan, Pakistan, Sri Lanka, and Malawi.
Turquoise is an opaque gem usually found in the blue-green colours which the name now denotes. It can also be found in other colours, varying from white to an unusual, yellowish green. It sometimes has flecks of pyrite or dark veins and spidery limonite lines.
Tuorquoise is rare and valuable, and its unusually beautiful colour has made it a prized gem and ornamental stone for many millennia.
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The word turquoise was coined in about the 16th century, from the French word either for ‘Turkish’ (Turquois), or ‘dark-blue stone’ (pierre turquin). Turquoise has been used extensively in the decorative tiles adorning Turkish places of worship and homes for many centuries. Quite possibly it is this association which caused the name to take root.
Because of its colour, the North American Indians believe that this gemstone opens up a direct connection between the sky and the sea.
Turquoise was among the very first gems to be mined, and although many historic sites have been depleted, a considerable number are still worked to this day. These are small-scale operations often worked on a seasonal basis, due to the size and remoteness of the deposits, largely worked by hand with little or no mechanization.
Turquoise has been used for fine jewellery by the rulers of Ancient Egypt, the Aztecs, Persia, Mesopotamia and in ancient China. Although it is one of the oldest gemstones, it did not become important as an ornamental stone in the West until the 14th century, when the decline of the influence of the Roman Catholic Church meant people felt able to use it in secular jewellery. It was introduced to India in the Mughal period (from 1526) and to Japan in the 18th century. In all these cultures it is believed that turquoise has certain prophylactic qualities – that it changes colour with the health of the wearer and protects him or her.
Turquoise has historically been used in combination with a variety of different gemstones. Ancient objects inlaid with turquoise include provocative and presumably ceremonial mosaic objects such as masks (some with a human skull as their base), knives and shields crafted by the Aztecs.
The iconic gold burial mask of Tutunkhamun is also inlaid with turquoise, lapis lazuli, and carnelian. The Persian style and use of turquoise in gold jewellery, often with rubies and diamond, was taken to India at the time of the Mughal Empire.
Persian turquoise was often engraved with devotional words in Arabic script inlaid with gold – the hardness of turquoise makes it an ideal material for carving in this way.
Turquoise treated like this can be found in buildings across India, such as the Taj Mahal.
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