Nahcolite
General
Category	Mineral
Chemical formula	NaHCO3
Strunz classification	05.AA.15
Dana classification	13.01.01.01
Identification
Crystal habit	Elongated crystals, fibrous masses, friable porous aggregates
Crystal system	Monoclinic prismatic
Twinning	Common on [101]
Cleavage	{101} perfect, {111} good, {100} distinct
Fracture	Conchoidal
Tenacity	Brittle
Mohs scale hardness	2.5
Luster	Vitreous - resinous
Streak	White
Diaphaneity	Transparent to translucent
Specific gravity	2.21
Optical properties	Biaxial (-)
Refractive index	nα = 1.377 nβ = 1.503 nγ = 1.583
Birefringence	δ = 0.206
Ultraviolet fluorescence	Short UV=blue-white cream-yellow, Long UV=cream-yellow
References	[1][2][3]

Nahcolite is a soft, colourless or white carbonate mineral with the composition of sodium bicarbonate (NaHCO₃) also called thermokalite. It crystallizes in the monoclinic system.^[3]

Nahcolite was first described in 1928 for an occurrence in a lava tunnel at Mount Vesuvius, Italy.^[1] The name is in reference to its chemical formula. It occurs as a hot spring and saline lake precipitate or efflorescence; in differentiated alkalic massifs; in fluid inclusions as a daughter mineral phase and in evaporite deposits.^[1][3]

It occurs in association with trona, thermonatrite, thenardite, halite, gaylussite, burkeite, northupite and borax.^[2] It has been reported in a Roman conduit at Stufe de Nerone, Campi Flegrei, near Naples; in the U. S. from Searles Lake, San Bernardino County, California; in the Green River Formation, Colorado and Utah; in the Tincalayu deposit, Salar del Hombre Muerto, Salta Province, Argentina; on Mt. Alluaiv, Lovozero Massif and Khibiny Massif, Kola Peninsula, Russia; and around Mount Erebus, Victoria Land, Antarctica.^[2]

[edit] References

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