Amber - Fossilised tree resin from pine trees, approx. 30 million years old.
Very Soft – 2 ½ Mohs'. very light. Avoid heat.
Colours – white, yellow, orange, brown, black, red, sometimes with insect inclusions.
Said to have healing powers and guard against witchcraft.
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Amethyst - A quartz gem. Quite hard – 7Moh’s, harder than steel.
Colours – purple, often heated to yellow (Citrine).
Most come from Brazil or Africa. Birthstone for February.
Said to protect against drunkenness. Has ecclesiastical preference.
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Aquamarine - Name means ‘sea water’. A beryl gem.
Colours – medium blue to greeny blue. Birthstone for March.
Said to have the ability to overcome the powers of darkness.
Most come from brazil or Madagascar.
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Bloodstone - A quartz gem – cryptocrystalline. Hardness is 7 Mohs' – harder than steel.
Deep opaque green with red patches. Used in signets and seals.
Used as amulet to stop bleeding.
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Citrine - A quartz gem. Hardness is 7 Mohs'.
Colours – yellow to sherry brown. Much is produced by heating Amethyst.
Colour similar to Topaz.
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Coral - Colours – red, pink, orange and white.
Dark red most desirable, pink “angels skin” 2nd most popular.
Skeletal remains of the coral polyp. Very soft – 3 ½ Mohs'.
Used as beads, cabochons and carvings. Thought to be lucky.
Found in the Mediterranean and Islands around Japan.
Said to be a cure for eye disease, to ward off panic and nightmares.
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Cornelian - A quartz gem – cryptocrystalline. Hardness is 7 Mohs'.
Used in signets and seals. Colour – reddish brown to yellowish red, orange.
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Cubic Zirconia - Man-made diamond stimulant.
Hardness 8 ½ Mohs' – will cut glass. Heavier than and similar fire to diamond.
Will not fade or change colour. Said to be the best diamond stimulant.
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Diamond - Made of pure carbon – same as lead in pencils.
Hardest natural gem – 10 Mohs'. Rare, beautiful with very high lustre called adamantine.
High level of fire (called dispersion).
Graded by 4C’s – colour, clarity, cut and carat weight.
Much is mined in Australia, South Africa, Russia, Rest of Africa. Also found in pale pastel colours
called fancy diamonds. Birthstone for April. Usually cut as a brilliant cut with 57 facets to best reflect light.
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Emerald - A beryl gem. Green – the deeper richer colours are the most desired.
Most have natural inclusions – those free from inclusions are rare and very valuable.
Hardness 7 ½ Mohs' but very brittle. Birthstone for may.
Said to help eyesight, and predict future if held under tongue.
Many are oiled to improve clarity and colour. Be careful with heat
Found in Columbia, Brazil, Siberia Zimbabwe, India and Pakistan.
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Garnet - Most seen in jewellery, is red but also occurs as green, yellow, orange.
Popular in Victorian jewellery especially as rose cut.
Said to offer protection from wounds, a symbol of life and to cure fever.
Hardness 7 ¼ Mohs'. Found in Sri Lanka and India.
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Jade - 2 different minerals – jadeite and nephrite.
Chinese consider jade lucky. Said to overcome fatigue and to prolong life. A symbol of love.
Colours – green, yellow, brown, black, orange, lilac and blue.
Found in New Zealand, Siberia, Burma, Japan and California.
Seen as carved figures, beads, and cabochons.
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Jet - Colour – black. Fossilised remains of trees (like coal).
Used by the Romans and Bronze Age man. Found in Whitby in the 19th century, also
Germany, Spain, USA and Russia. Used in Victoria mourning jewellery.
Takes a very high polish. Very light. Very soft - 3 ½ Mohs'.
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Lapis Lazuli - Colours – opaque blue with gold specks of iron pyrites, best is medium deep royal blue.
Best source is Afghanistan. Hardness 5 ½ Moh’s. Said to prevent melancholy.
Used as beads, signets, seals, cabochons, carvings.
Some is stained to improve colour. Do not immerse in liquid.
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Moonstone - Name comes from it’s appearance.
Colours – moonshine blue sheen from inside, white/colourless body. Hardness 6 Mohs'.
Found in Sri Lanka, India, Burma. A Lovers stone.
Foretell future when held in the mouth. Sacred in India.
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Opal - Silica gel with water. Soft nad brittle – 5 ½ - 6 on Mohs'.
3 main types – black has play of colour on dark background.
- white has play of colour on light background.
- fire is transparent orange with no play of colour.
Usually the more play of colour the better.
Birthstone for October. Said to protect from disease and make the wearer invisible. Opal
Doublets have a backing of black onyx or similar. Opal triplets have a black backing with
clear domed top. Most come from Australia and Brazil, fire opal from Mexico.
Porous so do not immerse. Avoid heat – it will dry out and crack.
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Peridot - Colour – olive green. Hardness 6 ½ Mohs'. Birthstone for August.
Found in the USA, Hawaii, Brazil and Isle of St.John in the red sea.
Said to be beneficial to the eyesight.
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Ruby - A Corundum gem. Very hard – 9 Mohs'. Quite heavy.
Colour – pink to deep red – best rubies are darker red, sometimes called “pigeons blood”.
Found in Burma, Thailand, Sri Lanka, Tanzania, Cambodia. Also found with a shimmering
Star effect reflecting from inside. Said to have an inextinguishable flame and to boil water.
Birthstone for July.
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Sapphire - A corundum gem. Very hard – 9 Mohs'.
Colours – blue, green, colourless, purple, green, yellow and pink. Very dark, almost black
from Australia, best said to be cornflower blue. Medium deep royal blue very desirable.
Said to denote wisdom, and an antidote to poison. Birthstone for September.
Found in Kashmir, Burma, Sri Lanka, Thailand and Australia. Also found with a shimmering
star effect from inside.
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Smokey Quartz - A quartz gem. Hardness – 7 Mohs'.
Colours – light to medium greyish brown to deep grey.
Most are from Brazil but some from Scotland and called Cairngorm.
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Spinel - Hardness 8 Mohs'.
Colour – red, blue, orange, lilac and pink.
Colourless are synthetic – man-made. Found in Burma, Sri Lanka, Tanzania, USA and Brazil.
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Tigers Eye - A quartz gem. Shows a cats eye effect that moves due to the reflection of light within the stone.
Colour – brown and golden. Used in signets, beads, seals, cabochon.
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Topaz - Hardness 8 Mohs'. colours – colourless, golden, blue, pink, red, brown.
Blue is usually irradiated Colourless material.
Found in Brazil, Madagascar, Sri Lanka. Birthstone for November. Said to aid eyesight.
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Tourmaline - Hard and durable – 7-7 ½ Mohs'.
Colours – pink, red, green and multi coloured. Also shimmering cats eye effect
Found in the USA, Sri Lanka, Madagascar, Kenya and Brazil (a kingfisher blue and electric
Green are found in Brazil – called Paraiba)
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Turquoise - Opaque and waxy. Colurs – pale green to greeny blue.
Found in Iran, Tibet, China and India.
Said to aid prosperity and freedom from depression and financial worry.
Hardness 6 Mohs'. often waxed and stained. Do not immerse in liquid.
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Zircon
- Hardness – 6 ½ - 7 ½ Mohs'. Heavy.
Colours – green, blue, yellow, orange and red. Also heat to blue, golden and colourless.
Found in Burma, Thailand and Sri Lanka. Said to protect against plague and injury,
And guard against lightening. An effective diamond stimulant. High Lustre and fire. Brittle,
may show signs or wear around facets called ‘paper wear’ so avoid contact with other gems and jewellery.
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gem@theassayoffice.co.uk