purpurite

from The Century Dictionary.

• noun A hydrous manganic ferric phosphate ((Mn,Fe)₂O₃.P₂O₅. H₂O) occurring in small irregular masses of a purple or dark red color: found in Gaston County, North Carolina, and also in San Diego County, California, and elsewhere.

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

• noun mineralogy A manganese phosphate mineral with a striking purple colour.