from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A mineral form of titanium dioxide, TiO2, having characteristic orthorhombic crystals and a red-brown to black color.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A dark brown mineral form of titanium dioxide, with the chemical formula TiO2.
from the GNU version of the Collaborative International Dictionary of English
- n. A mineral consisting of titanic oxide, and hence identical with rutile and octahedrite in composition, but crystallizing in the orthorhombic system.
from The Century Dictionary and Cyclopedia
- n. One of the three forms in which titanium dioxid occurs in nature.
Rutile is made up mostly of titanium dioxide with two rarer polymorphs anatase or octahedrite, which is a tetragonal mineral of pseudo-octahedral habit, and brookite, which is an orthorhombic mineral, the Doctor explained to her.
A set of specimens was exhibited by the Ellenville Zinc Company, consisting of strikingly beautiful crystalline masses of quartz galina, sphalerite and chalcopyrite and specimens of the rare mineral, brookite.