Several isolated crystal aggregates of the very rare borate mineral sborgite from one of the only three known localities worldwide: Furnace Creek, Inyo County, California, United States of America. — Photo: David Hospital · CC BY-SA 4.0
Sborgite
Sborgite is a sodium borate mineral with formula Na[B5O6(OH)4]·3H2O. The formula can be written as the oxide formulation, Na2O.5B2O3.10H2O. Sometimes called sodium pentaborate pentahydrate it contains the pentaborate anion, (B5O6(OH)4)−. Sborgite is colorless with monoclinic crystals. It was named for Umberto Sborgi, (1883–1955), Professor of Chemistry, University of Milan, Italy. Sborgite occurs in Tuscany, Italy and the Furnace Creek district, Death Valley, California, US.
Intro adapted from Wikipedia (CC BY-SA).
Sborgite is an IMA-recognized mineral species in the borate class, with the chemical formula NaB₅O₆(OH)₄·3H₂O.
It crystallizes in the monoclinic crystal system (space group C2/c).
Key properties: specific gravity 1.713; optically biaxial.
IMA symbol Srg, grandfathered status — known before the IMA’s founding, named in 1957.
Formed in pipes at a reduction works for borates from hot spring lagoons, between 32° C and 60° C (Larderello, Italy).
It is found associated with Borax, thénardite (Larderello, Italy); halite, thénardite (Furnace Creek district, California, USA).
The mineral was named to honor Professor Umberto Sborgi (1883–1955), Italian chemist, University of Milan, Milan, Italy, a worker in the system Na2 O−B2 O3 −H2O.