Kurnakovite

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Kurnakovite
Kurnakovite.jpg
Kurnakovite from Boron, California
General
Category Nesoborates
Formula
(repeating unit)
MgB3O3(OH)5·5H2O
Strunz classification 06.CA.20
Crystal symmetry Triclinic 1 pinacoidal
Unit cell a = 8.3479(1) Å, b = 10.6068(1) Å, c = 6.4447(1) Å; α = 98.846°, β = 108.981°, γ = 105.581°; Z = 2
Identification
Color White; colorless in transmitted light
Crystal habit Aggregates of prismatic crystals
Crystal system Triclinic
Twinning Twinning uncommon
Cleavage Poor to indistinct on {010}
Mohs scale hardness 2½ - 3
Luster Vitreous
Streak White
Diaphaneity Transparent to translucent
Specific gravity 1.847 - 1.852
Optical properties Biaxial (-)
Refractive index nα = 1.488 - 1.491 nβ = 1.508 - 1.510 nγ = 1.515 - 1.525
Birefringence δ = 0.027 - 0.034
2V angle Measured: 60° to 80°
References [1][2][3]

Kurnakovite is a hydrated borate mineral with the chemical composition MgB3O3(OH)5·5H2O. It is a member of the inderite group and is a triclinic dimorph of the monoclinic inderite.[2]

Discovery and occurrence[edit]

Kurnakovite, was first described by Godlevsky in 1940 for an occurrence in the Inder borate deposits in Atyrau Province, Kazakhstan, and is named for Russian mineralogist and chemist Nikolai Semenovich Kurnakov (1860–1941).[1]

In addition to the type locality in Kazakhstan, kurakovite has also been reported from the Zhacang-Caka brine lake, Tibet; the Kirka borate deposit, Kiitahya Province, Turkey; the Kramer borate deposit, Boron, Kern County, California; Death Valley National Park, Inyo County, California; and the Tincalayu borax deposit, Salar del Hombre Muerto, Salta Province, Argentina.[1][2]

Properties[edit]

Kurnakovite has triclinic - pinacodial crystallography. It forms as rough, prismatic crystals, typically in dense aggregates. Kurnakovite has distinct cleavage and a conchoidal fracture. Its tenacity is brittle and it ranges between 2.5 – 3 on the Mohs hardness scale. It is not soluble in water, though it will start dissolving in warm acid. Kurnakovite is usually colorless or white and either transparent or translucent. It has a vitreous, pearly luster and a refractive index of between 1.488 - 1.525.[1][2][3]

References[edit]