melanocerite

melanocerite

[¦mel·ə·nō′se‚rīt]
(mineralogy)
(Ca,Ce,Y)8(BO3)(SiO4)4(F,OH)4 A brown or black rhombohedral mineral composed of complex silicate, borate, fluoride, tantalate, or other anion of cerium, yttrium, calcium, and other metals; occurs as crystals.