Nahcolite

nahcolite

gaylussite

burkeite

thermonatrite

Images
Formula: NaH(CO3)
Carbonate
Specific gravity: 2.21
Hardness: 2½
Streak: White
Colour: Colourless, white, grey, buff
Solubility: Readily soluble in water and glycerine
Environments

Evaporite Deposits

Nahcolite is naturally occurring sodium bicarbonate. It is found as a precipitate from hot springs, as efflorescences around saline lakes and in brines, formed at a late stage in differentiated alkalic massifs, and as a solid in liquid inclusions in a variety of other mineral species. Associated minerals include trona, thermonatrite, thénardite, halite, gaylussite, burkeite, northupite and borax (HOM).

Localities

At the type locality, Mount Vesuvius, Metropolitan City of Naples, Campania, Italy, nahcolite has been found in a lava tunnel associated with halite and thénardite (Mindat).
Nahcolite from Mount Vesuvius - Image

At Stufe di Nerone, Pozzuoli, Metropolitan City of Naples, Campania, Italy, in old Roman conduit, nahcolite was found admixed with trona and thermonatrite as an efflorescence (Dana).

At Little Mogadi Dry Lake, Kajiado County, Kenya, nahcolite occurs as fibrous pseudomorphs after gaylussite, and as alteration rims around thermonatrite (Dana).

At Searles Lake, San Bernardino County, California, USA, nahcolite occurs in thin beds associated with gaylussite, thénardite, burkeite, northupite, borax and halite (Dana).
Nahcolite from Searles Lake - Image

At Anvil Points, Rifle, Garfield County, Colorado, USA, a number of underground openings have penetrated the high-grade oil-shale facies that contain the cavities, some of which were unleached and contain nahcolite, in crystalline, cleavable masses in concretions as large as five feet across and as small as a pea. It also was found in layers up to four inches thick intercalcated between oil-shale beds. The nahcolite in the concretions varies in colour from colourless, through white, yellow, brown and black. Most often the colour is a dirty brown because of the bitumen dispersed throughout the mineral.
The nahcolite occurring in the layers is pure white, translucent, and occurs as fibrous crystals at right angles to the bedding. It has a pearly opalescence and resembles the satin spar variety of gypsum (AM 32.117-120).
Nahcolite from Anvil Points - Image

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