leucopyrite

from The Century Dictionary.

• noun A mineral (Fe₃As₄) of a color between white and steel-gray and of a metallic luster, consisting chiefly of arsenic and iron. It is related to loellingite (FeAs₂) and arsenopyrite (FeAsS or FeAs₂.FeS₂).

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

• noun (Min.) A mineral of a color between white and steel-gray, with a metallic luster, and consisting chiefly of arsenic and iron.

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

• noun mineralogy An alternate name for löllingite.