Kernite

Kernite, also known as rasorite is a hydrated sodium borate hydroxide mineral with formula Na
2B
4O
6(OH)
2·3H
2O. It is a colorless to white mineral crystallizing in the monoclinic crystal system typically occurring as prismatic to acicular crystals or granular masses. It is relatively soft with Mohs hardness of 2.5 to 3 and light with a specific gravity of 1.91. It exhibits perfect cleavage and a brittle fracture.

Kernite
General
CategoryInoborates
Formula
(repeating unit)		Na
2B
4O
6(OH)
2·3H
2O
Strunz classification6.DB.05
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupP21/c
Unit cella = 7.0172(2)
b = 9.1582(2)
c = 15.6774(5) [Å]
β = 108.861(2)°; Z = 4
Identification
Formula mass273.22 g/mol
ColorColorless, white
Crystal habitCrystalline - occurs as well-formed coarse sized crystals
CleavagePerfect on [100] and [001], good on [201]
FractureSplintery
TenacityBrittle
Mohs scale hardness2.5-3
LusterVitreous - pearly
StreakWhite
Specific gravity1.9 - 1.92
Optical propertiesBiaxial (-)
Refractive indexnα=1.454, nβ=1.472, nγ=1.488
Birefringenceδ =0.0340
2V angle80°
Other characteristicsNon-radioactive, non-fluorescent, non-magnetic
References[1][2][3]

Kernite is soluble in cold water and alters to tincalconite when it dehydrates. It undergoes a non-reversible alteration to metakernite (Na
2B
4O
7·5H
2O) when heated to above 100 °C.[2]

Occurrence and history

The mineral occurs in sedimentary evaporite deposits in arid regions.

Kernite was discovered in 1926 in eastern Kern County, in Southern California, and later renamed after the county. The location was the US Borax Mine at Boron in the western Mojave Desert. This type material is stored at Harvard University, Cambridge, Massachusetts, and the National Museum of Natural History, Washington, D.C.[2]

The Kern County mine was the only known source of the mineral for a period of time. More recently, kernite is mined in Argentina and Turkey.[2]

The largest documented, single crystal of kernite measured 2.44 x 0.9 x 0.9 m3 and weighed ~3.8 tons.[4]

Uses

Kernite is used to produce borax which can be used in a variety of soaps.

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References
  1. Kernite WebMineral
  2. Handbook of Mineralogy
  3. Kernite on Mindat.org
  4. P. C. Rickwood (1981). "The largest crystals" (PDF). American Mineralogist. 66: 885–907.

Media related to Kernite at Wikimedia Commons

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