Nestolaite

Chemical formula: CaSe<sup>4+</sup>O<sub>3</sub>·H<sub>2</sub>O

Nestolaite is an extremely rare, hydrated calcium selenite, forming colorless, acicular crystals in the oxidation zones of selenium deposits.

## Characteristics Nestolaite is a hydrated calcium selenite, belonging to a group of very rare minerals. It occurs as microscopic, colorless to white crystals with an acicular or thin-prismatic habit. These crystals often form radial aggregates, fan-shaped clusters, or tangled, woolly masses on the surface of the host rock. Due to their small size, individual crystals are usually only visible under magnification. ## Physical Properties Nestolaite crystals exhibit a vitreous luster and are transparent. The density of the mineral has been calculated to be 3.11 g/cm³. Due to the small and fragile crystals, the Mohs hardness has not been measured. ## Colors and Varieties The mineral is typically colorless, less commonly white. No color or commercial varieties have been distinguished. ## History and Name Nestolaite was recognized as a new mineral species by the International Mineralogical Association (IMA) in 2016. Its formal description was published in 2017. The name honors Fabrizio Nestola (born 1972), professor of mineralogy at the University of Padua, Italy, for his contributions to crystallography and mineralogy. The type locality (place of discovery) is the Little Eva mine in the Yellow Cat area, Grand County, Utah, USA. ## Uses As an extremely rare mineral occurring in microscopic quantities, nestolaite has no industrial application. It is of purely scientific interest and is an object of interest for specialized collectors of rare minerals.

Properties

Luster
Vitreous
Streak
White
Density
3.11
Cleavage
Perfect on {010}
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Amateur identification of nestolaite is practically impossible. Its recognition requires advanced analytical techniques, such as X-ray diffraction (XRD) and chemical microanalysis (EDS), due to the microscopic size of the crystals and similarity to other secondary minerals. A key clue is its occurrence in paragenesis with other rare selenites in sandstone deposits. ## Distinguishing from Similar Minerals Nestolaite can be confused with other colorless, secondary selenium minerals, such as mandarinoite, olsacherite, or chalcomenite, as well as with microcrystalline gypsum (selenite). Definitive differentiation is only possible based on chemical and structural analysis. ## Crystal Forms It forms very small, acicular or thin, bladed crystals, elongated along one axis. They most often occur as radial or tangled aggregates, as well as coatings and crusts on the host rock.

Geological environment

## Genesis Nestolaite is a secondary mineral, forming in the oxidation zone of selenium deposits under low temperature and dry climate conditions. At the type locality, it formed in porous sandstone as a result of the weathering of primary selenium-bearing minerals. ## Mineral Associations This mineral coexists with other rare selenites. At the type locality, it was found in association with mandarinoite, olsacherite, chalcomenite, and gypsum (selenite variety). ## Localities Nestolaite is known almost exclusively from its discovery site – the Little Eva mine, in the Yellow Cat area, Grand County, Utah, in the United States. This is the only confirmed locality from which well-characterized specimens originate.

Rarity

Extremely rare

For collectors

## Quality Criteria As a microscopic mineral, the collector value of nestolaite is assessed based on different criteria than for macroscopic specimens. Samples with rich, dense clusters of well-formed, sharp crystals are most highly valued. The aesthetics of the aggregates (e.g., radial "sunburst" forms) and the presence of rare associated minerals on the same sample are also important. ## Popular Localities The only source of collector specimens is the historic type locality in Utah, USA. Material from this location is extremely difficult to obtain.

Care and storage

## Cleaning Nestolaite specimens are extremely delicate and sensitive. Cleaning should be kept to an absolute minimum. Only careful dust removal with a soft brush or a very gentle stream of compressed air from a safe distance is permissible. ## What to Avoid Contact with water and all chemical agents must be strictly avoided, as selenites can be partially soluble. The mineral is very brittle, so shocks, impacts, and any mechanical cleaning should be avoided. It should also be protected from high temperatures and humidity. ## Storage It is recommended to store specimens in closed, stable containers, preferably in "micromount" boxes, which protect against dust, mechanical damage, and sudden changes in ambient humidity.

Sources

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