Quartz and its large family
Quartz is one of the most common minerals on earth and is well known in the gems world. It’s a silicon dioxide.
Gemmology Species: Macrocrystalline Quartz Chemical composition: SiO, silicon dioxide Hardness: 7 (Mohs scale) Specific gravity: 2.65 Refractive index: 1.544 – 1.553
There are many colored quartz even though white or incolor quartz is by far the most common color.
Each color has its proper name.
Rock crystal: Colorless.
Smoky quartz: Brown to black, smoky gray.
Amethyst: Purple, violet, pale red-violet. Amethyst is the most highly valued stone in the quartz group.
Ametrine: Yellow and violet.
Citrine: Light yellow to dark yellow, gold-brown.
Prasiolite: Leek-green. Prasiolite is not found in nature. Prasiolite is produced by heat treatment of amethyst or yellowish quartz.
Rose quartz: Strong pink, pale pink.
Aventurine: Green, red-brown, gold-brown.
Quartz cat’s eye: White, gray, green, yellow, brown (Cat’s eye: Is a reflection of light by parallel fibers, needles, or channels, which resembles the slit eye of a cat. When the stone is rotated, the cat’s eye glides over the surface.)
Hawk’s eye: Blue-gray to blue green (Hawk’s eye: Small ray of light on the surface that is reminiscent of the eye of a bird of prey)
Tiger’s eye: Gold-yellow, gold-brown (Similar to Hawk’s eye effect, ray of light is brown colored due to oxidized iron inclusions)
Quartz with Rutile needles: Rock crystal containing rutile needles known as “Hair of Venus.” These very fine needles of rutile have an appearance generally golden, sometimes silvery, sometimes orange-red.
Dendritique quartz: inside is manganese dendrites forming plant with elegant graphics of a rare beauty.
Lodolite quartz: titanium, chlorum and iron
The deeper the color the most valuable is the stone.
Quartz location and deposits:
Rock crystal: In the Alps, Brazil, Madagascar, United States Smoky quartz: Brazil, Madagascar, Russia, Scotland, Switzerland, Ukraine Amethyst: Brazil, Bolivia, Canada, India, Madagascar, Mexico, Myanmar (Burma), Namibia, Russia, Sri Lanka, United States (Arizona), Uruguay and Zambia Ametrine: Brazil, Bolivia Citrine: Argentina, Brazil, Madagascar, Namibia, Russia, Scotland, Spain, United States Prasiolite: Brazil, United States (Arizona) Rose quartz: Brazil, India, Madagascar, Mozambique, Namibia, Sri Lanka, USA Aventurine: Austria, Brazil, India, Russia, Tanzania Quartz cat’s eye: Brazil, India, Sri Lanka Hawk’s eye: Brazil, India, Sri Lanka Tiger’s eye: Australia, India, Myanmar, Namibia, South Africa, Sri Lanka, United States
A few stories….
Chrysoprase, the bright apple green translucent chalcedony, was the favorite of Frederick The Great of Prussia. It can be seen today decorating many buildings in Prague, including the Chapel of St Wencelas.
Fine amethysts are featured in the British Crown Jewels and were also a favorite of Catherine the Great and Egyptian royalty. During middle age, amethyst was a favorite stone in the high ranks of the Christian church, therefore it was called “the stone of bishops”.