Tincalconite
Tincalconite is a hydrous
sodium borate mineral closely related to
borax, and is a secondary mineral that forms if borax as a dehydration product of borax. Its formula is Na
2B
4O
7·5H
2O or Na
6[B
4O
5(OH)
4]
3·8(H
2O).
Tincalconite typically occurs as a fine grained white powder. It crystallizes in the
hexagonal crystal system and has been found as primary euhedral di-rhombohedral, pseudo-octahedral crystals. It is also found
pseudomorphically replacing borax crystals. It has a
specific gravity of 1.88 and a
Mohs hardness of 2.
Refractive index values are nω=1.460 and nε=1.470.
While most tincalconite is created by man through exposing borax to dry air, there are natural occurrences of tincalconite, as in
Searles Lake,
California where it was first described in 1878. In addition to several California and Nevada locations it is reported from Argentina, Italy, Turkey and Ukraine.
The name comes from "tincal",
Sanskrit for borax, and Greek, "konis", meaning powder, for its composition and typical powdery nature.
* Palache, C., H. Berman, and C. Frondel (1951)
Dana's system of Mineralogy, (7th edition), v. II, pp.337â€"339.
*
Mineral Data Publishing, PDF*
Mindat with location data*
Webmineral data*
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