Rutile in Quartz
Itibiara, Bahia, Brazil
These golden, tetragonal crystals of rutile formed prior to the quartz crystal which later enveloped them. The finest specimens of rutilated quartz in the world come from this locality, which is Itibiara, Bahia, Brazil. The specimen has a polished surface and measures 10cm x 14cm. It was purchased from Sierra Nevada Minerals in 1987.
Rutile TiO2
Oxides; Titanium dioxide; may contain substantial amounts of iron
Color and Luster: Red, reddish brown, black; adamantine, submetallic; streak white, gray, pale brown
Hardness: 6-6.5
Cleavage: Distinct, sometimes good, two directions, poor in third
Fracture: Uneven, brittle
Crystals: Tetragonal; commonly long, striated prismatic crystals, knee-shaped and rosette twins; also acicular, compact, disseminated
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