Garnet is derived from the Latin word for pomegranate as they were thought to resemble the seeds of this fruit. The minerals are formed in nature at high temperatures/pressures. Garnet minerals are classified as a group. They crystallise in the cubic crystal system and are normally found in metamorphic rocks.
There are five basic garnet gem species, namely grossularite, pyrope, almandite, spessartite and andradite.
Garnets have a long folklore history tied to them. Garnets are believed to have powers of healing, strength and protection. Garnets assure the wearer of love, faithfulness, protection from evil, protection from terrifying dreams, safety from wounds and prevention of skin diseases. It was also thought that when danger approaches, the stone loses its brilliance.
The Egyptians used garnets as an antidote for snakebites, while it is thought that Noah hung a large garnet in the ark for illumination.
For obvious reasons red garnets have been associated with blood. As recently as 1892 native soldiers in the Kashmir Region fought the British with bullets made of garnet, in the belief that these would find their way magically to their targets. Asiatic tribes on the other hand, believed that it had a special affinity with blood and thus used rounded garnets as bullets in order to inflict a more serious wound when the garnet travelled through the bloodstream.
The 5 basic garnet gem species:
Pyrope is also known as ‘Cape Ruby’. It is a moderately valuable semi-precious gemstone, with the darkest crystals being the most common. Pyrope is usually red. It is coloured by iron and sometime by chromium. It does not fluoresce under ultraviolet light due to its iron content. However red spinel, which is similar, does.
Most pyrope, now used, is found in the diamond mines of South Africa. Russian pyrope is also of good quality. Other localities include Burma, Tanzania, Australia, Argentina and Brazil.
Brightly coloured almandine crystals, which are free of inclusions and internal cracks, are sometimes cut into gemstones. Although cut crystals have a brilliant luster, their transparency is often marred, even in clear stones due to an excessive depth of colour. Unlike rubies, the deep red colour does not lighten in natural light. Almandine is found in large quantities in sand deposits in Sri Lanka with lesser deposits occurring in Norway, Afghanistan, India, Madagascar, Tanzania, Brazil, Greenland and the USA.
The name is derived from the Spessart district of Germany, where the crystals were once found. Spessartine garnets are orange-pink, orange-red, red-brown or brownish-yellow in colour. They have a characteristic absorption spectrum, which is partly due to the presence of manganese.
Hessonite garnet is similar in colour but has quite different inclusion, which gives it a treacly appearance. Gem-quality examples are rare. Most of the crystals found in Germany and Italy are too small to be used in jewellery, but good examples are found in Australia, Burma, Madagascar, Norway and the USA.
Colour: Varies greatly. Can be green, yellowish-green, yellow-brown, red, orange, reddish-brown, pink, white, grey, and black Luster: Vitreous or resinous
Colours of streak: White
Transparency: Transparent to nearly opaque.
Cleavage: None
Fracture: Uneven to conchoidal
Tenacity: Brittle
Forms: Dodecahedral or trapezohedral crystals, also granular, compact or massive.
Varieties: Hessonite is yellowish-brown to orange-red with characteristic inclusions that look like swirls, giving a treacle-like appearance. Pure grossularite is colourless. “Transvaal Jade” is a massive variety from South Africa, and may be green, grey-blue or pink.
Uses: for gemstones
Occurrences: Occurs in a variety of metamorphic rocks, although most commonly in marble. Hessonite found in the gem grovels of Sri Lanka, and in Russia, Brazil, Canada and the USA. Green grossular garnet occurs in Tanzania and Kenya, and has been called “tsarvorite”.
Andradite has two varieties that have been used in jewellery. One is opaque black melanite, which has popularly been used in mourning jewellery. The other is green demantoid garnet, the colour of which is due to the presence of chromium. Melanine crystals are usually dodecahedra or icositetrahedra, or a mixture of both.
Demantoid is a rare variety of andradite. It has a higher dispersion than diamond, but the vivid green colour masks this property. It is relatively soft and so is not commonly used in jewellery.
Demantoid garnet looks red through the Chelsea Colour Filter and has a characteristic absorption spectrum with a strong bond in the red, which is due to iron. Inclusions are groups of radiating asbestos fibres that look like “horse-tails”. The main source for it is also found in Zaire and Korea, although these are not of such high quality.
Melanite is found in Italy and the Haute-Pyrenees of France. Topazolite is the name given to yellow andradite garnet.
The accepted birthstone to February is a pale lilac to nearly blackish-purple variety of the mineral quartz (SO2). Amethyst is mined in nearly all countries. The pale colours are often referred to as “Rose de France”. Those from Zambia and Russia show reddish flashes and are more highly valued than those with greyish overtones. Prices range for fine gems up to 5 carats, and can increase for larger gems. However, if the gem is larger than 25 carats, its price per carat decreases, as jewellers find it difficult to design with such large stones.
Amethyst varies in colour from pale violet to dark purple and may be particoloured with clear or yellow quartz. The tips of the crystals are often darkest and may grade to colourless quart. Amethyst is found lining hollow cavities in rocks. It changes colour with heat, and stones from different localities show different colour changes – to brown, yellow and sometimes even green. However, these changes are unpredictable and the colour may fade over time.
Amethyst has distinct dichroism, showing a bluish purple and a reddish purple. This distinguishes it from heat-treated stones that do not show any dichroism. Amethyst does not have a characteristic absorption spectrum. Inclusions are usually featherlike, or may resemble a thumbprint or tiger stripes.
Legend has it that the Greek god, Bacchus, in a drunken stupor, vowed to kill the first person he saw. Fatefully, the lovely maiden Amethyst passed by and Bacchus set loose a horde of wild beasts. Amethyst cried out to the goddess Diana, who could not stop the beasts, but used the only thing in her power to help Amethyst. She turned her into a statue of pure white marble. When Bacchus realised what he had done, he repented and threw the last of his wine over the statue, which immediately turned a beautiful purple colour. “Amethyst” comes from from the Greek word for “not drunken,” and the gem was believed to protect from the effects of wine, especially if the stone was held under the tongue while drinking.
Placed under the pillow, amethysts are said to ensure pleasant dreams, improve memory and provide immunity from poison. Some people believe that a wearer of this stone will become gentle and amiable.
Amethyst has played a part in religion since ancient Egypt. It was the ninth gem in the breastplate of the high priest of Israel, and the gem of the Tribe of Dan. It has long been used in bishops’ rings, and its purple colour adorns the garments of church officials and kings.
Aquamarine, together with emerald and beryl, belongs to the beryl group. It is so named because of its seawater colour, but a sky blue stone is the most desired. Lower qualities are heated to change them to the preferred aquamarine blue. It is more frequently transparent than emerald. Aquamarine is brittle and sensitive to pressure. Its pigment is iron and typical inclusions are fine hollow rods that sometimes reflect white light. Where growth lines are present in larger numbers, a cat’s eye effect, or even asterism with a six-rayed star, is possible. In the past (and even sometimes today) aquamarine was believed to be a talisman for sailors.
Because of inclusions of foreign substances, physical properties of aquamarine can vary. The chemistry of aquamarine is quite complex and difficult to duplicate, thus, synthetic aquamarine is scarce and expensive. There are aquamarine deposits in all of the continents, however, the most important ones are in Africa and South America. These continents are also the greatest sources for aquamarine.
Fine quality aquamarines in the 2ct range are priced depending on their clarity and colour. Mozambique aquamarines usually show strong dark blue colours, while those from Brazil come in all shades of blue.
Aquamarine was extensively used in ancient Greek jewellery and was also discovered in Egyptian tombs of 2000 BC. It is said to protect sailors and heal broken relationships.
The name of diamonds comes from the Greek “Adam”, meaning “invincible,” or “the unconquerable”. It is the hardest known material on earth and consists only of carbon. Diamond is relatively scarce and has unique optical and physical properties greatly desired by man. For centuries it has attained an allure unsurpassed by other gems.
Diamonds were first mined in the 4th Century in Golconda, Southern India. In 1730, they were also discovered in Brazil, but remained rare gems worn only by rulers and aristocracy. In 1866, much larger deposits were discovered in South Africa, where the industry soon became monopolised and the era of mass consumption dawned. The tradition of the diamond as a symbol of engagement is said to have begun when Archduke Maximillian of Austria gave a diamond to Mary of Burgundy, his wife to be.
De Beers made diamonds a household name by using the slogan, “a diamond is forever.” It became one of the most famous slogans of the 20th Century.
The normal colour of diamond is pale to dark yellow or brown. Ninety percent of the world’s production is of industrial quality i.e. opaque, and is used as abrasives or in cutting tools. Gem-quality diamonds are transparent and are cut and polished to enhance their beauty. The size, colour, clarity and the quality of cut determine the value of each gem.
The appearance of diamonds (their colour and inclusions) may be improved through the technology of man. Fractures can be filled with resin, while dark inclusions can be removed by laser drilling. High temperature, high-pressure techniques are available to remove the brown colour of a colourless, brown or pink diamond with almost undetectable amounts of trace elements.
When valuing gem diamonds, one must consider the “four C’s”. These are colour, cut, clarity and carat.
Diamonds are found in all colours. Mostly they are yellowish to white, or brownish. More rarely they have strong colours (green, red, blue, violet, brown, yellow) that are grouped together as “fancy colours” and, in quality gems, fetch collector’s prices.
The rarity of a diamond also depends on how free it is of inclusions and external blemishes. These imperfections are identified under 10x magnification and plotted on the grading report.
Even though diamonds are the hardest natural substance known to man, they are precious and deserve to be cared for.
Here are some tips to keep your diamonds as beautiful as the day you first laid eyes on them:
Emerald is the birthstone for May. Trace amounts of chromium and vanadium are responsible for the rich green colour that has made emerald one of the world’s most sought-after gems.
The earliest deposits were located south of Cairo in Cleopatra’s mines. Spanish conquistadores discovered emeralds in Colombia in the 1500s. Today, these deposits are still regarded as the highest in value. Other sources of emeralds are Brazil, Zambia and Afghanistan.
Emeralds are seldom eye-clean. They normally contain a variety of inclusions that help the gemologist to identify their country of origin. Cubic pyrite and white calcite inclusions along fractures suggest a Colombian origin, while thin, needle-like inclusions of tremolite are typical of emeralds from Zimbabwe. Inclusions in emerald are often tree or moss-like. Jewellers often term this characteristic, “jardin”, which is the French word for “garden”. An abundance of inclusions, especially in larger gems, will obviously affect their brilliance and lower the value.
Emerald, together with aquamarine and beryl, belongs to the beryl group, being the most precious of the group.The value of an emerald is based mainly on its colour, and, if it is a large gem, its purity. The saturated, intense green is the most highly valued.
The majority of emeralds have been enhanced. This enhancement can be achieved through oiling, thus improving their colour and clarity, or filling their fractures with resin to make the inclusions less visible. These enhancements must be disclosed to potential buyers.
Emeralds have been synthesized since the start of the 20th Century. Hydrothermal flame fusion and flux-grown processes are often used to produce synthetic emeralds, which are normally named after their creator or the process used.
The emerald was discovered in ancient times, and, because of its long history, it has been shrouded by much lore and mysticism.
Many cultures throughout time believed the emerald had enormous power. It was believed that the owner of an emerald would be able to see into the future, strengthen his or her memory, or become an eloquent speaker. Green was regarded as the colour most beneficial to sight and the placement of emeralds on the eyelids was believed to improve vision. Emeralds were also linked to fertility and the earth goddess as well as the goddess, Venus. In the past, it was worn by women to ease childbirth and has also been said to stifle epileptic fits.
Various civilisations had their own point of view on what the emerald stood for. The Chaldeans believed the stone contained a goddess. The Egyptians believed the emerald stood for fertility and rebirth. In some legends it is believed that the Holy Grail was fashioned from an emerald.
Ruby is thus named because of its red colour (from the Latin, “Rubeus”). It was not until about 1800 that ruby, as well as sapphire, was recognized as belonging to the corundum group.
The colouring pigment of rubies is chrome and, for brown hues, some iron may be added. It is not possible to determine the source area of a ruby from its colour, as each deposit yields various tones. The most desirable colour is so called “pigeon’s blood”, which is pure red with a hint of blue. The distribution of colour is often uneven, and may appear in stripes or spots. The more intense the colour is the more expensive the gem is. Slight variations in colour can affect value dramatically. Secondary colors of purple and orange may detract from the price, whereas pinkish overtones may increase the value. Size is also important, as large fine gems are quite rare.
Rubies from the Magok in Burma are considered the finest due to their intensely saturated red colour, or “pigeon’s blood” colour. Other sources are from Thailand, Pakistan, East Africa, Madagascar and Vietnam.
Nearly all rubies have been heat-treated to improve their colour and clarity. Recently, a high temperature process (whereby the elements beryllium and chromium are infused into the crystal structure) has been developed which dramatically improves the colour of rubies. The red colour of such gems is located only in its outer layer and, when chipped or repolished, the colourless interior may become visible. These enhancements can easily be detected by a gemologist and should be disclosed to the client.
Ruby has long been recognized as a valuable gem. In Sanskrit, it is described as “ratnaraj”, the “king of gems”, and in the Bible, it is mentioned as one of the gems in the breastplate of the high priest. The famous 170ct Black Prince Ruby, mounted as a center piece in the Imperial State Crown of England, is not a ruby at all, but a natural rough crystal of red spinel.
Historically, ruby is associated with royalty and the power over life and death. They are also considered to represent devotion, desire and passion. In the distant past, rubies were attributed the power to prevent loss of blood and strengthen the heart.
Peridot was brought to Europe by the crusaders in the Middle Ages and was often used for ecclesiastic purposes. It was very popular during the baroque period. It is not greatly desired by the trade because of its lower hardness.
The most important deposits of peridot are into the Red Sea on the volcanic island of St John, they have been mined there for 3500 years. Beautiful crystals can be found on the walls of the volcano cavities of weathering peridot rocks. There are also quarries in upper Burma. Less important finds have been in Australia, Brazil, South Africa, the US and Zaire.
Peridot is the gem variety of the mineral olivine, a magnesium and iron silicate. It is one of the few gemstones that occur in one colour. It has a vitreous and greasy luster and is not resistant to sulphuric acid. It tends to burst under great stress, therefore is sometimes metal-foiled. Dark stones can be lightened through burning. Rarities are peridot cat’s eye and star peridot.
Peridot is not a tough stone and is best reserved for jewellery other than rings. It should be set with care and not exposed to heat.
To the ancients the Peridot was the “Gem of the sun”. Pirates believed that a peridot had the power to drive evil spirits away. Other myths include its ability to clean and heal the heart and to turn dreams in to reality.
Peridot is associated with the astrological sign of Libra and is assigned to the sun. In ancient Hebrew writings this stone is linked with the tribe of Simeon. Peridot is believed to cure liver disease and dropsy, to free the mind of envious thoughts, and to dispel terrors of the night. It is believed for its full magical power to arise it needs to be set in gold.
The name has been traced to the Sanskrit word “Sanipriya” meaning “dear to the planet Saturn”.
When Prince Charles gave Diana Spencer an 18ct royal blue Ceylon Sapphire engagement ring, the gem received worldwide attention and Lady Di’s ring became a “must have” item. The most important loose sapphire is probably the Star of India, a 563ct, semi-round double cabachon on display at the American Museum of Natural History in New York.
Sapphire is mined in more than a dozen countries. Those from Kashmir in India have a milky, velvety, saturated blue colour, often described as cornflower and are highly sought-after. From Burma came the dark blue sapphire close in value to those from Kashmir. Sri Lanka produces sapphire in all pastel colours. A special variety with a pinkish-orange colour is called padparadscha and is the highest priced of all sapphires. Thailand and Australia produce extremely dark blue sapphires which sometimes have a greenish tint. Kenya, Zambia and recently Madagascar are modern sources of sapphires of all colours, which are normally darker than those from Sri Lanka. The Yogo Mine in Montana, USA, is famous for it’s untreated, natural blue sapphires. India is also a famous source for star sapphire in black, grey to purplish colours.
The value of sapphire is mainly dependent on colour, but if it’s Kashmir origin is certified, the price may double. Visible colour banding and the presence of inclusions will also affect the value.
Nearly all sapphires are heat-treated to enhance their colour and clarity. Cracks may be filled with a borat glass. When “cooked” in a melt containing iron and titanium, these elements will diffuse into the crystal structure of the sapphire and render the outside skin of the gem a darker colour. Yellow sapphires are sometimes irradiated and may lose their colour if exposed to intense light. These enhancements must be disclosed to prospective buyer. Ninety-nine percent of Kashmir and Vogo Gulch (USA) sapphires are untreated — thus their exceptional prices.
Sapphires are traditionally connected with the eye and the sky and therefore with vision and the ability to read the future. Sapphires render black magic harmless and help the wearer discern falsehood and guile. The rulers in ancient Persia believed the sky was blue due to the reflection of sapphire stones, while some religions believed the blue colour of sapphires represented the heavens.
Tourmaline is a group of closely related minerals with a very complex chemistry. It was first discovered by Dutch traders off the West coast of Italy in the late 1600’s or 1700’s. Its name derives from the Singhalese word, “turmallu,” meaning “mixed colours”.
The complex chemistry of tourmaline results in most unusual colours, as well as some quite unique properties. In the 18th Century, Professor W. Goodchild described that, when tourmaline is heated to 150 degrees Celsius, one end of the crystal becomes positively charged, while the other end obtains a negative electric charge. This characteristic is called “piezoelectricity”, which causes the unusual attraction tourmaline has for dust.
All continents produce tourmaline, but the most important sources are the deposits near Karibib in Namibia, Tanzania, Madagascar, Maine USA, Minas Gerais in Brazil and in Sri Lanka.
Pink and red (also rubellite) tourmalines are the most sought-after. Although they tend to be more included than the other colours, they are normally more expensive than the greens and blues. Namibia and Sri Lanka are the most important sources of these gems.
Green tourmaline is the most common variety, and its colour varies from olive green to bluish-green. It is called “verdelite”.
Blue tourmaline is called “indicolite”, and is quite rare. It can fetch up to US% 250/ct.
An unusual electric blue tourmaline was discovered a few decades ago near Paraiba, Brazil. Copper is the element that causes the unusual blue colour. Paraiba tourmaline is the most expensive tourmaline. Most of these gems weigh less than a carat. Much larger Curich tourmalines with less saturation, thus of lesser value, come from Mozambique.
Brown (dravite), colourless (achroite) and black (schorl) tourmalines are seldom used in jewellery. Particoloured tourmalines contain more than one colour that fades into each other.
Colour combinations are endless, from green/red, yellow-green/purple and greenish-blue/orange-red. A special type of tourmaline has a pink to red core and a green outer rim. This is often cut into slices across the length of the crystal and is appropriately called “watermelon tourmaline”.
Legend tells us that tourmaline is found in all colours as it travelled along a rainbow and gathered all it’s lovely hues from it. Other beliefs include tourmaline’s power to strengthen the body and spirit and to inspire creativity.
Topaz is an aluminium silicate containing some fluorine and hydroxyl. Although topaz comes in many colours, blue is the most popular. All colours of topaz are accepted as the birthstone for November.
The name topaz may come from the Greek word “topazos”, meaning “to seek”, or perhaps from the Sanskrit word “tapas”, meaning “yellow fire”. The most sought-after topaz has a reddish-yellow colour, often referred to as “Imperial topaz”. Topaz is mined on all continents, with Brazil, USA, Mexico and Sri Lanka being the main producers. The original Imperial topaz comes from Brazil.
Topaz is usually devoid of inclusions that can be seen with the naked eye and occurs in very large sizes. The largest recorded facetted topaz, weighs more than 40 000cts. Its colour can vary from colourless (called “silver topaz”), to light blue, golden yellow, orange-yellow, brown, red, light green and pink.
Certain colourless topazes can be irradiated and heated to produce different shades of blue. Light coloured blues are called “Swiss blue”. Moderately dark blues are called “American Blue” or “sky blue”. While the darker ones are referred to as “London Blue” A recent method by which trace elements are diffused into the topaz crystal structure produces beautiful, intense green topaz, which has the trade name “Evergreen Topaz”.
Topaz is quite hard and can withstand scratches better than most coloured gems, including emerald and quartz. However, it has a perfect basal cleavage along which the gem will split if incorrect pressure is applied. Gem setters must therefore be careful when setting a topaz. They should know that gem cutters normally position the cleavage direction at a 10 — 15 degree angle to the table facet.
Turquoise is present in ancient history. For example Egyptian priests and nobility wore turquoise carvings and beads 6 000 years ago. The mummy of King Tutankhamen (1 370 — 1 352 BC), was richly decorated by turquoise inlays and scarab carvings.
It is also thought that Turquoise could have been America’s first currency, as it played an important role in Native American culture dating back to 700BC. Persia was, for centuries, the world’s foremost source. Writings from the 12th Century BC indicate that Isaac, the son of Abraham, opened mines at Neyshabur in the North Eastern mountains of Persia. Some are still in operation and are known as the Isaac mines. Turquoise jewellery became fashionable during the reign of Queen Victoria.
Turquoise is a massive opaque, green to blue, copper aluminium phosphate mineral, which is used in beads, cabochons, carvings and inlays. The name probably derives from “Turkish Stone” which could have referred to the Persian turquoise trade route that passed through Turkey.
Two varieties of turquoise are considered desirable. Both types have a pure blue colour that is described as “robin’s egg”. The traditional, and specifically, the eastern fabourite, is a pure, even-coloured gem with a high polish. Buyers from the new world prefer to see a web-like veining (called spider webbing) spread evenly throughout the stone.
Turquoise is formed in a host rock that is either black or brown. This host material is called “matrix”, which occurs as veins in the gem.
The price of turquoise depends mainly on its colour and, t a lesser degree, its lustre. Lustre is affected by hardness and density. Softer and porous material cannot be polished to produce the required lustre. The hardness of turquoise can vary from 2 to almost 6 on the Mohs Hardness Scale, while its specific gravity can vary between 2.6 — 2.9.
Inferior qualities will have a pale greenish-blue colour and will feel lighter. Its surface may be pitted, with polish lines and a dull finish. In ancient times, turquoise was more valuable then gold. Large fine quality gems (20ct plus) are rare.
There are four methods to improve the quality of turquoise: Centuries ago, turquoise was immersed in animal fat to give it a desired “wet” look.
Stailisation is a process where porous turquoise is impregnated with a colourless epoxy resin that will harden the stone, allowing a better polish.
Colour enhancement is obtained by mixing a dye with the epoxy.
Reconstructed turquoise is made by compressing pulverized turquoise and epoxy resin to look like the real thing.
