| Nahcolite | |
|---|---|
 Nahcolite from California (size: 9.5 x 8 x 4 cm) | |
| General | |
| Category | Carbonate mineral |
| Formula (repeating unit) | Sodium bicarbonate (NaHCO3) |
| IMA symbol | Nah |
| Strunz classification | 5.AA.15 |
| Dana classification | 13.01.01.01 |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (same H-M symbol) |
| Space group | P21/n |
| Unit cell | a = 7.47, b = 9.68 c = 3.48 ; β = 93.38°; Z = 4 |
| Identification | |
| Colour | White to colourless, may be grey to brown |
| Crystal habit | Elongated crystals, fibrous masses, friable porous aggregates |
| Twinning | Common on |
| Cleavage | {101} perfect, {111} good, {100} distinct |
| Fracture | Conchoidal |
| Tenacity | Brittle |
| Mohs scale hardness | 2.5 |
| Lustre | 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 |
| Solubility | Soluble in water |
| References | |
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.
Nahcolite was first described in 1928 for an occurrence in a lava tunnel at Mount Vesuvius, Italy. Its name refers to the elements which compose it: Na, H, C, and O. 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.
It occurs in association with trona, thermonatrite, thenardite, halite, gaylussite, burkeite, northupite and borax. It has been reported in a Roman conduit at Stufe de Nerone, Campi Flegrei, near Naples; in the United States 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.
References
- Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
- ^ Nahcolite on Mindat.org
- ^ Nahcolite in the Handbook of Mineralogy
- ^ Nahcolite data on Webmineral
- Richard V. Gaines, H. Catherine W. Skinner, Eugene E. Foord, Brian Mason, and Abraham Rosenzweig: Dana's new mineralogy, John Wiley & Sons, 1997
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