Trona

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Trona specimen - rock identification

What is Trona?

Trona (trisodium hydrogendicarbonate dihydrate, also sodium sesquicarbonate dihydrate, Na2CO3•NaHCO3•2H2O) is a non-marine evaporite mineral. It is mined as the primary source of sodium carbonate in the United States, where it has replaced the Solvay process used in most of the rest of the world for sodium carbonate production.

Etymology & Origins

The word entered English by way of either Swedish (trona) or Spanish (trona), with both possible sources having the same meaning as in English. Both of these derive from the Arabic trōn, which in turn derives from the Arabic natron, and Hebrew נטרן‎ (natruna), which comes from ancient Greek νιτρον (nitron), derived ultimately from ancient Egyptian ntry (or nitry'’).

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North ZoneCentral RidgeSouth Basin

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Key Characteristics

Composition of Trona

The crystal structure of trona was first determined by Brown et al. (1949). The structure consists of units of 3 edge-sharing sodium polyhedra (a central octahedron flanked by septahedra), cross-linked by carbonate groups and hydrogen bonds. Bacon and Curry (1956) refined the structure determination using two-dimensional single-crystal neutron diffraction, and suggested that the hydrogen atom in the symmetric (HC2O6) anion is disordered. The environment of the disordered H atom was later investigated by Choi and Mighell (1982) at 300 K with three-dimensional single-crystal neutron diffraction: they concluded that the H atom is dynamically disordered between two equivalent sites, separated from one another by 0.211(9) Å. The dynamically disordered H atom was reinvestigated at low temperature by O'Bannon et al. 2014 and they concluded that it does not order at temperatures as low as 100K.

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Trona specimen 2
© E65vern

Quick Facts

Physical Properties

Color
Colourless, gray-white, light yellow; colourless in transmitted light.
Hardness (Mohs)
2.5
Density
2.14 g/cm³

Chemical Properties

Chemical Formula
Na3H(CO3)2 · 2H2O
Elements
C, H, Na, O
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