Nishanbaevite

Chemical formula: KAl₂O(As₅+O₄)(S₆+O₄)

Nishanbaevite is a very rare potassium aluminum arsenate-sulfate, forming microscopic, colorless tabular crystals.

## Characteristics Nishanbaevite is a mineral from the sulfate and arsenate group, chemically a hydrated potassium aluminum sulfato-arsenate. It occurs as extremely small, tabular or lath-like crystals, which rarely exceed 40 micrometers in length and a few micrometers in thickness. The crystals are colorless and transparent, often forming irregular aggregates or rosette-like clusters on the surface of other minerals. ## Physical Properties Due to the microscopic size of the crystals, most of nishanbaevite's physical properties have not been fully determined. Hardness is too difficult to measure but is estimated to be low. The density calculated from the formula and unit cell parameters is 3.33 g/cm³. The mineral exhibits a vitreous luster. ## Colors and Varieties Nishanbaevite is colorless. No colored varieties or trade names are known. ## History and Name The mineral was discovered in the dumps of a former arsenic and gold mine in the Piskom region of northeastern Uzbekistan. It was approved by the International Mineralogical Association (IMA) in 2020 under the number IMA2020-040. The name honors Tursunmurat Nishanbaevich Nishanbaev (born 1951), an Uzbek geologist and mineralogist, specialist in arsenic and gold deposits in the Tien Shan region, where the mineral was found.

Properties

Luster: Vitreous
Streak: White
Density: 3.33
Cleavage: None
Fracture: Uneven
Transparency: Transparent
Crystal system: Monoclinic

Diagnostic features

## Identification Identification of nishanbaevite is impossible without advanced analytical techniques. It requires the use of a scanning electron microscope (SEM) with EDS analysis to determine chemical composition and X-ray diffraction (XRD) to confirm the crystal structure. Visually, at the occurrence site, it may be suspected as microscopic, colorless, vitreous coatings in association with other rare arsenates. ## Distinguishing from Similar Minerals Visually, it is indistinguishable from many other secondary minerals, such as gypsum, anhydrite, or other rare sulfates and arsenates that form microscopic crystals. Definitive differentiation is possible only through chemical and structural analysis. ## Crystal Forms Crystals have the form of thin, flattened tablets or laths, often with hexagonal or octagonal outlines. They usually form irregular, rosette-like, or radial aggregates.

Geological environment

## Genesis Nishanbaevite is a fumarolic mineral. It forms as a result of the reaction of volcanic gases rich in arsenic and sulfur with surrounding rocks in a high-temperature environment. At the type locality (Uzbekistan), it crystallized on the surface of sandstones in a volcanic exhalation zone. ## Mineral Associations This mineral co-occurs with other rare products of volcanic exhalations. In its immediate vicinity, anhydrite, alunite, realgar, orpiment, as well as other rare arsenates such as dmisokolovite, piskovite, and uzbekistanite, have been found. ## Localities The only confirmed locality for nishanbaevite in the world is its type locality - the area of the former mine in the Piskom mountains, in the Ohangaron district, Tashkent Province, Uzbekistan.

Rarity

Extremely rare

For collectors

## Quality Criteria As a microscopic mineral, nishanbaevite is valued primarily for the mere fact of its presence on a specimen. The most highly rated samples are those where the crystals, despite their small size, form distinct, rich aggregates, and their identity has been analytically confirmed. Contrast with the matrix and co-occurrence with other rare minerals from this locality also increase the specimen's value. ## Popular Localities The only source of specimens is the type locality in Uzbekistan. Material from this location is extremely difficult to obtain and appears on the collector's market sporadically.

Care and storage

## Cleaning Specimens containing nishanbaevite should be handled with utmost care due to their extreme rarity and microscopic nature. Cleaning is not recommended, as mechanical methods (brushes, compressed air) can easily damage or dislodge the delicate crystals. Rinsing in water, especially distilled water, may be safe, but all chemicals should be avoided. ## What to Avoid Contact with acids and other aggressive chemicals should be strictly avoided. Specimens should not be subjected to ultrasonic cleaning. Due to its genesis in a volcanic environment, it may be sensitive to changes in humidity and temperature, although precise data are not known. ## Storage The safest way to store specimens is to place them in a sealed, padded "micromount" box to protect them from dust, shocks, and mechanical damage. Exposure should be away from direct sunlight and heat sources.

Sources

IMA Mineral List (CNMNC)