tungstite

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A yellow or yellowish-green mineral, essentially WO₃, often occurring with tungsten ores.

from The Century Dictionary.

• noun Native oxid of tungsten, occurring in pulverulent form, of a bright-yellow color, usually in connection with wolfram, the tungstate of iron and manganese. Also called tungstic ocher.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Min.) The oxide of tungsten, a yellow mineral occurring in a pulverulent form. It is often associated with wolfram.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun mineralogy An orthorhombic hydrous tungsten oxide mineral formed by the weathering of other tungsten-containing minerals.