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Kernite

Kernite
General
Category Inoborates
Formula
(repeating unit)
Na
2
B
4
O
6
(OH)
2
·3(H
2
O)
Strunz classification 06.DB.05
Crystal symmetry Monoclinic prismatic
H-M symbol: (2/m)
Space group: P 21/c
Unit cell a = 7.0172(2) Å, b = 9.1582(2) Å, c = 15.6774(5) Å, β = 108.861(2)°; Z=4
Identification
Formula mass 273.22
Color Colorless, white
Crystal habit Crystalline - occurs as well-formed coarse sized crystals
Crystal system Monoclinic
Cleavage Perfect on [100] and [001], good on [201]
Fracture Splintery
Tenacity Brittle
Mohs scale hardness 2.5-3
Luster Vitreous - pearly
Streak white
Specific gravity 1.9 - 1.92
Optical properties Biaxial (-)
Refractive index nα=1.454, nβ=1.472, nγ=1.488
Birefringence δ =0.0340
2V angle 80°
Other characteristics non-radioactive, non-fluorescent, non-magnetic
References [1][2][3]

Kernite, also known as rasorite is a hydrated sodium borate hydroxide mineral with formula Na
2
B
4
O
6
(OH)
2
·3(H
2
O)
. 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 is soluble in cold water and alters to tincalconite when it dehydrates. It undergoes a non-reversible alteration to metakernite (Na
2
B
4
O
7
·5(H
2
O)
) 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.

References

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

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