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Gemstone Properties:   Achroite   Actinolite   Alexandrite   Almandine   Amber   Amethyst   Ametrine   Andradite   Andalusite   Apache Tear   Apatite   Aquamarine   Axinite   Barite   Benitoite   Beryl   Bixbite   Bytownite   Calcite   Cassiterite   Cerussite   Chrysoberyl   Citrine   Clinozoisite   Cordierite    Corundum   Cubic Zirconia   Danburite   Demantoid   Diamond   Diopside   Dravite   Ekanite   Elbaite   Emerald   Epidote   Euclase   Feldspar   Fluorite   GGG   Garnet   Goshenite   Gypsum   Hauynite   Heliodor   Hiddenite   Indicolite   Idocrase   Iolite   Kornerupine   Kunzite   Kyanite   Labradorite   Moldavite   Morganite   Obsidian   Opal   Orthoclase   Padparadschah   Peridot   Petalite   Piemontite   Phenacite   Prasiolite   Quartz   Rhodochrosite   Rhodolite   Rubellite   Ruby   Sapphire   Scapolite   Scheelite   Selenite   Sinhalite   Sphalerite   Sphene   Spinel   Spodumene   Schorl   Spessartite   Sunstone   Tanzanite   Topaz   Topazolite   Tourmaline   Tektite   Tsavorite   Verdelite   Vesuvianite   Wulfenite   YAG   Zincite   Zircon   Zoisite  
Quartz (silicon dioxide)
Color: Colorless, gray, brown, yellow, orange, violet, red-violet, pink and leek green.

Type/Color:

Amethyst - Violet to red-violet.

 
Bolivian Amethyst
Uruguayan Amethyst
 Rose d' France Amethyst
from Brazil

Citrine - Light yellow, amber, orange to deep red-brown and golden-brown.

 
Uruguayan Irai Citrine
Australian Oxblood Citrine

Ametrine  - Combination of amethyst and citrine in one stone.

Rock Crystal - Colorless

Rose Quartz - Pink
Smoky - Light-brown to black to smoky gray.

Prasiolite (Green Quartz) - Leek-green

Often incorrectly called green amethyst.

 
Green Quartz (irradiated)

Oro Verde Quartz - Yellow-green.

Oro Verde Quartz (irradiated)

Moh’s hardness: 7

Refractive index: 1.544-1.553

Critical angle: 40°

Specific gravity: 2.63-2.65

Cleavage: None

Fracture: Conchoidal, brittle.

Dispersion: Medium (.013)

Heat sensitivity: Low

Pleochroism: Amethyst: very weak (purple to grayish purple); Natural citrine: weak (yellow to light-yellow); Prasiolite: very weak (light-green to paler green); Rock crystal: colorless, no dichroism; Rose quartz: weak (pink to paler pink); Natural dark smoky: definite (brown to reddish-brown).

Birefringence (double refraction): Weak (.009)

Crystal structure: Hexagonal

Treatments: Oro Verde, lemon citrine, smoketrine and most dark gray smoky quartz without any brown tones are all irradiated.  Citrines are often heat treated to improve color and give a reddish tint.  Most citrine is amethyst that has been heat treated.  Some smoky can be heated to create citrine.  Prasiolite is heat treated amethyst and citrine from one locality.

Cutting: Quartz cuts easily.  Pre-polishing with 1200 Nubond or 3000 standard lap will make polishing much quicker and more enjoyable.

Polishing: Cerium oxide on most common polishing laps.

Comments: Blue colored quartz is available as a synthetic.  Beware that nearly a quarter of all commercial cut amethyst is synthetic.  Synthetic citrine and ametrine are also being sold as natural by unscrupulous dealers.

Gemstone Properties:   Achroite   Actinolite   Alexandrite   Almandine   Amber   Amethyst   Ametrine   Andradite   Andalusite   Apache Tear   Apatite   Aquamarine   Axinite   Barite   Benitoite   Beryl   Bixbite   Bytownite   Calcite   Cassiterite   Cerussite   Chrysoberyl   Citrine   Clinozoisite   Cordierite    Corundum   Cubic Zirconia   Danburite   Demantoid   Diamond   Diopside   Dravite   Ekanite   Elbaite   Emerald   Epidote   Euclase   Feldspar   Fluorite   GGG   Garnet   Goshenite   Gypsum   Hauynite   Heliodor   Hiddenite   Indicolite   Idocrase   Iolite   Kornerupine   Kunzite   Kyanite   Labradorite   Moldavite   Morganite   Obsidian   Opal   Orthoclase   Padparadschah   Peridot   Petalite   Piemontite   Phenacite   Prasiolite   Quartz   Rhodochrosite   Rhodolite   Rubellite   Ruby   Sapphire   Scapolite   Scheelite   Selenite   Sinhalite   Sphalerite   Sphene   Spinel   Spodumene   Schorl   Spessartite   Sunstone   Tanzanite   Topaz   Topazolite   Tourmaline   Tektite   Tsavorite   Verdelite   Vesuvianite   Wulfenite   YAG   Zincite   Zircon   Zoisite  
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