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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.

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