Trona

Trona
Trona sample
General
Category	Carbonate mineral
Formula (repeating unit)	Na2CO3•NaHCO3•2H2O
Strunz classification	5.CB.15
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Identification
Color	Colorless or white, also grey to yellowish grey
Crystal habit	Columnar, fibrous and massive.
Cleavage	[100] perfect, [111] and [001] indistinct
Fracture	Brittle - subconchoidal
Mohs scale hardness	2.5
Luster	Vitreous
Streak	White
Diaphaneity	Translucent
Specific gravity	2.11 - 2.17
Optical properties	Biaxial (-)
Refractive index	nα = 1.412 nβ = 1.492 nγ = 1.540
Birefringence	δ = 0.128
Solubility	Soluble in water
Other characteristics	May fluoresce under short wavelength ultraviolet
References

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.

The word "trona" 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).

Trona is found at Owens Lake and Searles Lake, California; the Green River Formation of Wyoming and Utah; the Makgadikgadi Pans in Botswana and in the Nile Valley in Egypt. The trona near Green River, Wyoming, is the largest known deposit in the world and lies in layered evaporite deposits from 800 to 1,600 feet (240 to 490 m) below ground, where the trona was deposited in a lake during the Paleogene Period. Trona has also been mined at Lake Magadi in the Kenyan Rift Valley for nearly 100 years. The northern part of Lake Natron is covered by a 1.5 m thick trona bed, and occurs in 'salt' pans in the Etosha National Park in Namibia. The Beypazari region in the Ankara Province of Turkey has some 33 trona beds in two fault-bound lensoid bodies in and above oil shales of the Lower Hirka Formation (16 in the lower and 17 in the upper body). The Wucheng basin trona mine, Henan Province China has some 36 trona beds (693–974 m deep), the lower 15 beds are 0.5–1.5 m thick, thickest 2.38 m; the upper 21 beds are 1–3 m thick, with a maximum of 4.56 m hosted and underlain by dolomitic oil shales of the Wulidui Formation.

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Wikipedia