DANBURITE
Danburite is a calcium borosilicate mineral (CaB2(SiO4)2)
that shares many of the same physical properties with topaz. It has a
nonmetallic, glassy luster, ranges in color from clear to white to gray to
yellow to brown to pink, has a white streak, is quite hard (H = 7 to 7.5), and
has long, prismatic crystals with poor cleavage (cf. good cleavage in
topaz). Danburite has been reported from contact metamorphosed
limestones, metamorphosed evaporites, hydrothermal veins, and occurs in some
granites.
Danburite from the La Aurora Mine, San Luis Potosi, Mexico (CSM # 53641,
Colorado School of Mines Geology Museum, Golden, Colorado, USA).