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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

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 - Leek-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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