Kernite
Hydrated sodium borate mineral used to produce borax.
Kernite, also called rasorite, is a hydrated sodium borate hydroxide mineral. Its chemical formula is Na2B4O6(OH)2·3H2O. This mineral is colorless to white and forms in the monoclinic crystal system, usually appearing as prismatic or needle-like crystals, or as granular masses. It is fairly soft, rating between 2.5 and 3 on the Mohs scale, and has a low specific gravity of 1.91. Kernite shows perfect cleavage and breaks in a brittle manner.
It dissolves in cold water and, when it loses water, transforms into tincalconite. Heating kernite above 100 °C causes an irreversible change into metakernite (Na2B4O7·5H2O).
Kernite is found in sedimentary evaporite deposits in dry regions. It was first identified in 1926 in eastern Kern County, Southern California, and later named after that county. The discovery site was the US Borax Mine at Boron in the western Mojave Desert. Type specimens are kept at Harvard University in Cambridge, Massachusetts, and the National Museum of Natural History in Washington, D.C. For a time, the Kern County mine was the only known source of kernite. More recently, it has also been mined in Argentina and Turkey. The largest single crystal ever documented measured 2.44 by 0.9 by 0.9 meters and weighed about 3.8 tons.
Kernite is used to make borax, which is an ingredient in various soaps.
- field
- Mineralogy
- known_for
- Source of borax used in soaps
- hardness
- 2.5 to 3 (Mohs)
- specific_gravity
- 1.91
- crystal_system
- Monoclinic
Lore & Background
Kernite, also called rasorite, is a hydrated sodium borate hydroxide mineral that forms in sedimentary evaporite deposits within arid regions. It typically appears as colorless to white crystals, often prismatic or needle-like in shape, and can also occur as granular masses. The mineral crystallizes in the monoclinic crystal system and is relatively soft, with a Mohs hardness between 2.5 and 3, and notably light, having a specific gravity of 1.91. It displays perfect cleavage and a brittle fracture. Kernite is soluble in cold water and, when it loses water, it alters to tincalconite. Heating the mineral above 100 °C causes a non-reversible transformation into metakernite. Discovered in 1926 in eastern Kern County, Southern California, it was later renamed after the county. The original discovery site was the US Borax Mine at Boron in the western Mojave Desert. Type specimens are preserved at Harvard University and the National Museum of Natural History in Washington, D.C. For a time, the Kern County mine was the only known source of kernite, but more recently it has also been mined in Argentina and Turkey. The largest documented single crystal of kernite measured 2.44 by 0.9 by 0.9 meters and weighed approximately 3.8 tons. The mineral is used to produce borax, which is employed in various soaps.
Reader's Guide
Kernite is significant as a mineral source of borax, which is used in a variety of soaps. The mineral occurs in sedimentary evaporite deposits in arid regions, and its largest known crystal weighed approximately 3.8 tons. While initially only found in Kern County, subsequent mining in Argentina and Turkey expanded its availability. The mineral's perfect cleavage and brittle fracture, along with its low hardness and specific gravity, define its physical characteristics. Its legacy lies in its role as a borax ore, supporting industrial applications, and its type specimens preserved in major museums.
Did You Know?
- Kernite is also known as rasorite.
- The largest documented single crystal of kernite weighed about 3.8 tons.
- Kernite alters to tincalconite when it dehydrates.
Frequently Asked Questions
What is Kernite?
Kernite, sometimes called rasorite, is a hydrated sodium borate hydroxide mineral with the chemical formula Na₂B₄O₆(OH)₂·3H₂O. It belongs to the mineralogy field and is best known as a borax-bearing species.
What does Kernite look like in hand specimens?
It typically presents as colorless to white prismatic or acicular crystals, though granular masses are also common. The mineral crystallizes in the monoclinic system, giving its crystals a distinctly angular, non-cubic appearance.
How hard and heavy is Kernite?
Kernite sits at a Mohs hardness of roughly 2.5 to 3, making it soft enough to scratch with a copper penny or a fingernail in some cases. Its specific gravity is only 1.91, so it feels notably light for a mineral, and it shows perfect cleavage with a brittle fracture.
Why is Kernite important to industry?
Its primary practical role is serving as a natural source of borax, which is then processed into products such as soaps and other household cleaning agents. Without borate minerals like Kernite, the borax supply chain would lack one of its key raw-material inputs.
How does Kernite differ from other borate minerals?
Kernite is distinguished by its specific hydrated sodium-borate hydroxide composition and its monoclinic prismatic habit, setting it apart from more common borates like ulexite or colemanite. Its relatively low hardness and light specific gravity also make it easier to identify in the field than harder borate species.
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