The Mineral KERNITE

  • Chemistry: Na2B4O6(OH)2-3H2O, Hydrated Sodium Borate Hydroxide
  • Class: Carbonates
  • Subclass: Borates
  • Uses: an ore of boron and as mineral specimens.
  • Specimens

Kernite, like other borates, is a structurally complex mineral. The basic structure of kernite contains chains of interlocking BO3(OH) tetrahedrons. The chains' basic unit has a formula of B4O6(OH)2 and a charge of negative two (-2). Connected to the chains are triangular BO3 groups with the sodiums and water molecules interspersed between the chains.

Kernite could be considered a metamorphic mineral as it is thought to form from the recrystallization of borax due to mild heat and pressure. The mineral borax is directly deposited in arid regions from the evaporation of water in intermittent lakes called playas. The playas form only in rainy seasons due to runoff from adjacent mountains. The runoff is rich in the element boron and is highly concentrated by evaporation in the arid climate. Eventually the concentration is so great that crystals of borax and other boron minerals form and accumulate to great thickness. Kernite is found at the bottom of these deposits in stratified units with some kernite crystal layers growing several feet thick.

Individual crystals can be quite transparent and appear similar to certain gypsum crystals. However, kernite is harder and forms splintery cleavage fragments. Specimens of kernite are interesting, and can make a good addition to one's collection.


  • Color is white or gray to colorless.
  • Luster is vitreous to greasy.
  • Transparency crystals are transparent to translucent.
  • Crystal System is monoclinic; 2/m
  • Crystal Habits include short prismatic crystals, but is more commonly found in parallel aggregates resembling vein minerals.
  • Cleavage is perfect in two directions forming splintery fragments.
  • Fracture is splintery due to cleavage.
  • Hardness is 2.5 - 3 (harder than a fingernail)
  • Specific Gravity is approximately 1.9+ (very low density)
  • Streak is white.
  • Associated Minerals are borax, ulexite, hydroboracite and other borate minerals.
  • Other Characteristics: slightly soluable in water.
  • Notable Occurrences include several localities in Kern Co., California, USA; Chile, and Turkey.
  • Best Field Indicators are crystal habit, associations, locality, density, splintery cleavage, and hardness.
KERNITE specimens:
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KERNITE specimen ker-1
$ 45.00
Dims: 2.5 x 1.3 x 0.6" (6.4 x 3.4 x 1.5 cm)
Wt: 1.2 oz. (35 g)
U.S. Borax Mine, Kern County, California, U.S.A.
A section of a prismatic Kernite crystals makes up this hand specimen. Though a few areas show obvious cleavage, it does not have the compact, fibrous habit of most such specimens. Even so, its monoclinic prismatic form is warped, likely due to intergrowth. The piece is colorless, transparent and moderately clear, containing internal fractures and dark green-gray inclusions, and has a waxy luster on its uncleaved areas and a greasy-to-pearly luster on its cleaved ones. There is no host rock present.
no photo
ker-1 ($ 45.00)
U.S. Borax Mine, Kern County, California, U.S.A.
KERNITE specimen ker-2
$ 30.00
Dims: 5.8 x 1.9 x 0.8" (14.7 x 4.7 x 2.0 cm)
Wt: 4.6 oz. (132 g)
Boron, Kern County, California, U.S.A.
This Kernite aggregate is in very good condition, showing little human-induced damage. Though no actual crystals are discernable, its crystalline habit is relatively well-defined, showing the standard parallel striations. It has the standard milky-white color and matte luster of the specie, and is dimly transparent. There is no host rock present.
no photo
ker-2 ($ 30.00)
Boron, Kern County, California, U.S.A.


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