Quartz
Hot Springs, Arkansas
This specimen measures 18cm x 21cm
Quartz SiO2
Silicates; Silicon dioxide
Color and Luster: White, colorless, and in various shades as follows: rockcrystal, transparent, colorless; amethyst, purple, rose quartz, pink, rose-red; citrine, clear yellow; smoky quartz, plae brown to black; milky quartz, milk white; aventurine, glistening with enclosed scales of mica or hematite; cat's eye, opalescent from inclusions of asbestos; and tigereye, with lusterous yellow to brown parallel fibers; vitreous, greasy luster; streak white
Hardness: 7
Cleavage: Generally none; rarely indistinct rhombohedral parting
Fracture: Conchoidal
Crystals: Hexagonal; usually prismatic crystals striated crosswise and frequently terminated by double rhomohedrons(like hexagonal pyramids); also granular, disseminated, massive
Photo by Mary Sutherland
Descriptions taken from
The Audubon Society Field Guide to North American Rocks and Minerals