Kurnakovite is a hydrated borate mineral

Borate mineral

The borate minerals are minerals which contain a borate anion group. The borate units may be polymerised similar to the SiO4 unit of the silicate mineral class. This results in B2O5, B3O6, B2O4 anions as well as more complex structures which include hydroxide or halogen anions...

 with the chemical composition MgB₃O₃(OH)₅·5(H₂O). It is a member of the inderite group and is a triclinic dimorph

Polymorphism (materials science)

Polymorphism in materials science is the ability of a solid material to exist in more than one form or crystal structure. Polymorphism can potentially be found in any crystalline material including polymers, minerals, and metals, and is related to allotropy, which refers to chemical elements...

 of the monoclinic inderite.

Discovery and occurrence

Kurnakovite, was first described by Godlevsky in 1940 for an occurrence in the Inder borate deposits in Atyrau Province

Atyrau Province

Atyrau Oblast is a province of Kazakhstan. It is situated in the west of the country around the northeast of the Caspian Sea. Its capital is the city of Atyrau, with a population of 142,500 people; the province itself has 480,000 people...

, Kazakhstan

Kazakhstan

Kazakhstan , officially the Republic of Kazakhstan, is a transcontinental country in Central Asia and Eastern Europe. Ranked as the ninth largest country in the world, it is also the world's largest landlocked country; its territory of is greater than Western Europe...

, and is named for Russian mineralogist and chemist Nikolai Semenovich Kurnakov

Nikolai Semenovich Kurnakov

-Biography:Kurnakov was born in Nolinsk, Kirov Oblast. He attended a high school at Nizhny Novgorod and later studied at the mining institute in St. Petersburg. He published his first paper on alum crystallization and sodium thioantimoniate in 1882. In the same year he graduated as a mining engineer...

 (1860-1941).

In addition to the type locality

Type locality (geology)

Type locality , also called type area or type locale, is the where a particular rock type, stratigraphic unit, fossil or mineral species is first identified....

 in Kazakhstan, kurakovite has also been reported from the Zhacang-Caka brine lake, Tibet

Tibet

Tibet is a plateau region in Asia, north-east of the Himalayas. It is the traditional homeland of the Tibetan people as well as some other ethnic groups such as Monpas, Qiang, and Lhobas, and is now also inhabited by considerable numbers of Han and Hui people...

; the Kirka borate deposit, Kiitahya Province, Turkey

Turkey

Turkey , known officially as the Republic of Turkey , is a Eurasian country located in Western Asia and in East Thrace in Southeastern Europe...

; the Kramer borate deposit, Boron, Kern County, California

Kern County, California

Spreading across the southern end of the California Central Valley, Kern County is the fifth-largest county by population in California. Its economy is heavily linked to agriculture and to petroleum extraction, and there is a strong aviation and space presence. Politically, it has generally...

; Death Valley National Park

Death Valley National Park

Death Valley National Park is a national park in the U.S. states of California and Nevada located east of the Sierra Nevada in the arid Great Basin of the United States. The park protects the northwest corner of the Mojave Desert and contains a diverse desert environment of salt-flats, sand dunes,...

, Inyo County, California

Inyo County, California

-National protected areas:* Death Valley National Park * Inyo National Forest * Manzanar National Historic Site-Major highways:* U.S. Route 6* U.S. Route 395* State Route 127* State Route 136* State Route 168* State Route 178...

; and the Tincalayu borax deposit, Salar del Hombre Muerto, Salta Province

Salta Province

Salta is a province of Argentina, located in the northwest of the country. Neighboring provinces are from the east clockwise Formosa, Chaco, Santiago del Estero, Tucumán and Catamarca. It also surrounds Jujuy...

, Argentina

Argentina

Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...

.

Properties

Kurnakovite has triclinic - pinacodial crystallography. It forms as rough, prismatic crystals, typically in dense aggregates. Kurnakovite has distinct cleavage

Cleavage (crystal)

Cleavage, in mineralogy, is the tendency of crystalline materials to split along definite crystallographic structural planes. These planes of relative weakness are a result of the regular locations of atoms and ions in the crystal, which create smooth repeating surfaces that are visible both in the...

 and a conchoidal fracture

Conchoidal fracture

Conchoidal fracture describes the way that brittle materials break when they do not follow any natural planes of separation. Materials that break in this way include flint and other fine-grained minerals, as well as most amorphous solids, such as obsidian and other types of glass.Conchoidal...

. Its tenacity

Tenacity

Tenacity is the customary measure of strength of a fiber or yarn. In the U.S. it is usually defined as the ultimate strength of the fiber divided by the denier....

 is brittle

Brittle

A material is brittle if, when subjected to stress, it breaks without significant deformation . Brittle materials absorb relatively little energy prior to fracture, even those of high strength. Breaking is often accompanied by a snapping sound. Brittle materials include most ceramics and glasses ...

 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

Lustre (mineralogy)

Lustre is a description of the way light interacts with the surface of a crystal, rock, or mineral. The word lustre traces its origins back to the Latin word lux, meaning "light", and generally implies radiance, gloss, or brilliance....

 and a refractive index

Refractive index

In optics the refractive index or index of refraction of a substance or medium is a measure of the speed of light in that medium. It is expressed as a ratio of the speed of light in vacuum relative to that in the considered medium....

of between 1.488 - 1.525.