TINCALCONITE
Tincalconite is a hydrous sodium hydroxy-borate
mineral (Na2B4O5(OH)4·3H2O).
It often forms as a result of dehydration (removal of some water) of other
borate minerals, such as borax (Na2(B4O7)·10H2O).
Tincalconite has a nonmetallic luster that is dull to glassy in some
specimens. It is quite soft (H=2) and has a white, powdery
appearance. It usually takes on the crystal form of the pre-alteration
mineral.
Tincalconite taking on the crystal forms of the precursor mineral, borax (i.e.,
tincalconite pseudomorphs after borax).
Locality:
Boron, southeastern Kern County, southern California, USA.
(CSM # 75.28, Colorado School of Mines Geology Museum,
Golden, Colorado, USA)