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
Category	Inoborates
Formula (repeating unit)	Na 2B 4O 6(OH) 2·3H 2O
Strunz classification	6.DB.05
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	P21/c
Unit cell	a = 7.0172(2) b = 9.1582(2) c = 15.6774(5) [Å] β = 108.861(2)°; Z = 4
Identification
Formula mass	273.22 g/mol
Color	Colorless, white
Crystal habit	Crystalline - occurs as well-formed coarse sized crystals
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 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.

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