Aksaite

Chemical formula: MgB<sub>6</sub>O<sub>7</sub>(OH)<sub>6</sub>·2H<sub>2</sub>O

A rare hydrated magnesium borate, forming white aggregates within salt domes.

## Characteristics Aksaite is a mineral from the borate group, chemically a hydrated magnesium borate. It most often occurs in the form of spherical or irregular aggregates and concretions, composed of fine, tangled fibers or grains. More rarely, it forms radial aggregates. Well-formed crystals are sporadically found and usually appear as small, acicular or prismatic columns. ## Physical Properties This mineral is relatively soft, with a Mohs hardness of 2.5-3. It exhibits a vitreous luster, and in the case of fibrous aggregates, a silky luster. It is transparent to translucent. Its density is low, ranging from 2.06 to 2.11 g/cm³. ## Colors and Varieties Aksaite is most often colorless, white, or grayish-white. No color or commercial varieties are distinguished. ## History and Name The mineral's name comes from its discovery location – the Ak-say (Aksai) valley in Kazakhstan, which in Kazakh means "white valley" or "white stream". It was first described in 1963 by the Russian mineralogist V.V. Lobanova. ## Applications Due to its rarity, aksaite has no industrial application. It is solely an object of scientific interest and is valued by advanced mineral collectors.

Properties

Mohs hardness
2.5-3
Luster
Vitreous, Silky
Streak
White
Density
2.06-2.11
Cleavage
Perfect on {010}, good on {100}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Orthorhombic

Diagnostic features

## Identification Characteristic features of aksaite include its occurrence in paragenesis with other evaporite minerals, low hardness, low density, and form of occurrence (white, fibrous or granular nodules and concretions). The silky luster in fibrous aggregates is also a helpful indicator. ## Distinguishing from Similar Minerals Aksaite can be confused with other white borates, such as ulexite, colemanite, or inyoite, as well as with gypsum. It is harder than gypsum (gypsum has a hardness of 2). It is much softer than colemanite (hardness 4.5). Ulexite often exhibits the characteristic "television stone" optical effect, which is absent in aksaite. Final differentiation usually requires advanced studies, e.g., X-ray diffraction (XRD) analysis. ## Crystal Forms Crystals are rare, acicular or short-prismatic. This mineral mainly forms compact, granular, fibrous, radial aggregates, as well as concretions and crusts.

Geological environment

## Genesis Aksaite is a secondary mineral, formed under specific conditions within evaporite deposits. It forms in gypsum-anhydrite caps covering salt domes (diapirs). ## Mineral Associations It most often co-occurs with other minerals formed under similar conditions, such as halite, gypsum, anhydrite, and also with other borates, e.g., inyoite, colemanite, and preobrazhenskite. ## Localities The most important and classic locality for aksaite, from which the best specimens originate, is the Chelkar salt dome in the Ak-say valley, Atyrau Region, Kazakhstan. This is its type locality and the main source of specimens worldwide.

Rarity

Very rare

For collectors

## Quality Criteria Specimens with well-formed, even if small, transparent crystals are most highly valued by collectors. Rich crystalline aggregates and aesthetic associations with other rare borates also have high value. Due to the general rarity of the mineral, even amorphous but massive fragments are sought after. ## Popular Localities The vast majority of collector specimens come from the only significant locality in the world – the Chelkar salt dome in Kazakhstan.

Care and storage

## Cleaning Aksaite specimens should only be dry-cleaned, using a soft brush to remove dust. Contact with water can lead to damage or dissolution of the mineral. ## What to Avoid Contact with water, acids, and other chemicals should be strictly avoided. The mineral is sensitive to moisture, so it should not be stored in humid rooms. As a soft mineral, it is susceptible to scratches. ## Storage It is recommended to store specimens in a dry, stable environment, preferably in a closed display box or cabinet with a desiccant. It should be isolated from harder minerals to avoid mechanical damage.

External references

Sources

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