triplite

from The Century Dictionary.

• noun A mineral occurring in brownish-red crystalline masses, often fibrous. It is essentially a fluophosphate of iron and manganese.

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

• noun (Min.) A mineral of a dark brown color, generally with a fibrous, massive structure. It is a fluophosphate of iron and manganese.

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

• noun mineralogy A rare manganese-bearing phosphate mineral.