THE MINERAL NAHCOLITE

Chemistry: NaHCO₃ , Sodium Bicarbonate.
Class: Carbonates
Uses: Only as mineral specimens.
Specimens

Nahcolite is one of those rare minerals that are named for their chemistry. In this case, straight from its formula: NaHCO₃. Simply replace the (3) with (-lite) and you get nahcolite! There are similarly named minerals such as cavansite which stands for calcium vanadium silicate; nahpoite for its formula Na₂H(PO₄); nacaphite for being a sodium (Na) calcium (Ca) phosphate and the inverse canaphite for calcium (Ca) sodium (Na) phosphate. The HCO₃ ion in nahcolite's formula is called bicarbonate and is composed of one hydroxide which has taken the place of one of the three oxygens on a normal carbonate ion, CO₃. NaHCO₃ is also known chemically as "baking soda". Nahcolite forms large concretionary masses in the oil-shales of the Green River Formation and as an evaporite mineral in non-marine sedimentary deposits. Nahcolite was first discovered as a mineral at Searles Lake, California in 1940 and forms several beds in the lake sediments, some up to two feet thick. Nahcolite can absorb water and specimens should be stored in closed containers.

PHYSICAL CHARACTERISTICS:

Color is colorless, white, brown or gray.
Luster is vitreous.
Transparency: Crystals are transparent to translucent.
Crystal System is monoclinic; 2/m.
Crystal Habits include prismatic crystals, but usually massive crusts.
Cleavage: There is a perfect cleavage.
Hardness is 2.5.
Specific Gravity is 2.2 (well below average)
Streak is white.
Associated Minerals include other sedimentary evaporite minerals such as hanksite, gaylussite, analcime, halite, pirssonite, northupite, borax and calcite.
Notable Occurrences include Searles Lake, San Bernardino County and Deep Spring Lake, Inyo County, California and the Green River Formation, Colorado, USA; Egypt and Lake Magadi, Kenya.
Best Field Indicators: Environment of formation, cleavage, density, crystal habit and locality.