Tourmaline (Elbaite)
Pala, California
This specimen measures 7cm x 4.5cm
Tourmaline group Na(Mg,Fe)3Al6(BO3)3(Si6O18)(OH,F)4
Cyclosilicates; complex silicate of boron and aluminum, whose composition varies widely because of substitutions
Color and Luster: Black(Schorl), blue, pink and red(Elbaite), brown(Dravite), green, multicolored, rarely white; vitreous, streak white
Hardness: 7-7.5
Cleavage: None
Fracture: Uneven, conchoidal
Crystals: Hexagonal, usually short to long prismatic crystals that commonly have a rounded triangular cross section, striated lengthwise; also radiating, columnar, compact
Note: Specimen donated by W. C. Sherwood
Photo by Mary Sutherland
Descriptions taken from
The Audubon Society Field Guide to North American Rocks and Minerals