Quartz crystal

General

Category: Silicate mineral

Formula (repeating unit): SiO2)

Strunz classification: 04.DA.05

Dana classification: 75.01.03.01

Crystal symmetry: Trigonal 32

Unit cell: a = 4.9133 Å, c = 5.4053 Å; Z=3

Identification

Color: Colorless through various colors to black

Crystal habit: 6-sided prism ending in 6-sided pyramid (typical), drusy, fine-grained to microcrystalline, massive

Crystal system: α-quartz: trigonal trapezohedral class 3 2; β-quartz: hexagonal 622

Twinning: Common Dauphine law, Brazil law and Japan law

Cleavage: {0110} Indistinct

Fracture: Conchoidal

Tenacity: Brittle

Mohs scale hardness: 7 – lower in impure varieties (defining mineral)

Luster: Vitreous – waxy to dull when massive

Streak: White

Diaphaneity: Transparent to nearly opaque

Specific gravity: 2.65; variable 2.59–2.63 in impure varieties

Optical properties: Uniaxial (+)

Refractive index: nω = 1.543–1.545 nε = 1.552–1.554

Birefringence: +0.009 (B-G interval)

Pleochroism: None

Melting point: 1670 °C (β tridymite) 1713 °C (β cristobalite)

Solubility: Insoluble at STP; 1 ppmmass at 400 °C and 500 lb/in2 to 2600 ppmmass at 500 °C and 1500 lb/in2

Other characteristics: Piezoelectric, may be triboluminescent, chiral (hence optically active if not racemic)


Flickr page for this photo.

Visit the Eye for Science Flickr group.

Get the "Eye for Science" widget here and install it on your own blog. Spread the scienticity!

Like this image? Want it for your smartphone wallpaper?
Use this QR Code to load it on your smartphone and enjoy!