Pyrite and Quartz
Spruce Peak, King County, Washington
This specimen is 22 cm. wide and 13 cm. high; the largest cube measures 6.5 cm. on edge. It is from the classic Spruce Peak, King County, Washington locality. The specimen was collected by John Medici. The JMU Museum purchased it from him in 1982.
Pyrite FeS2
Sulfide; Iron disulfide, often with substantial amounts of nickel and cobalt
Color and Luster: Pale yellow to brass-yellow, often tarnished with brown film of iron oxide; sometimes iridescent; metallic; streak greenish black
Hardness: 6-6.5
Cleavage: None
Fracture: Uneven, brittle
Crystals: Isometric; predominantly in cubes and pyritohedrons with parallel striations of faces, less commonly in octahedrons; also in nodules and massive forms; fine to coarse granular, fibrous, mammillary, stalactitic
Pyrite is the most common iron sulfide mineral, and is often referred to as "fool's gold" in allusion to its gold color and metallic luster.
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, pale 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 lustrous 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 rhombohedrons(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