Sharyginite

Chemical formula: Ca₃Ti⁴⁺Fe³⁺₂O₈

Sharyginite is a rare oxide from the brownmillerite group, forming microscopic, dark brown crystals in specific, thermally altered calcareous rocks.

## Characteristics Sharyginite is an oxide mineral belonging to the brownmillerite subgroup. It occurs as very small, tabular or lath-like crystals, usually not exceeding 20 micrometers in length. It forms aggregates in association with other minerals within thermally altered fragments of calcareous rocks. Its dark brown color and microscopic scale make it an object of primarily scientific study, rather than a typical collector's mineral. ## Physical Properties This mineral is characterized by a hardness in the range of 5.5-6 on the Mohs scale. It is opaque, with a brown streak. Its density, calculated based on the chemical formula and unit cell parameters, is 3.943 g/cm³. It exhibits good cleavage in one direction. ## Colors and Varieties Sharyginite occurs in a uniform, dark brown color. No color varieties or commercial names are known. ## History and Name The mineral is named in honor of Russian geologist and petrologist Viktor Sharygin (born 1965), a specialist in high-temperature petrology and studies of inclusions in minerals. It was approved as a new mineral by the International Mineralogical Association (IMA) in 2012 (IMA2012-052). The type locality, from which sharyginite was first described, is the Caspar quarry in Ettringen, in the Eifel region of Germany. ## Applications Due to its rarity and microscopic crystal size, sharyginite has no industrial applications. It is solely an object of scientific interest and is valued by specialized collectors of rare minerals (so-called micromounts).

Properties

Mohs hardness: 5.5-6
Luster: Metallic
Streak: Brown
Density: 3.943
Cleavage: Good on (010) and imperfect along (001) and (100).
Fracture: Irregular/Uneven
Transparency: Opaque
Crystal system: Orthorhombic

Diagnostic features

## Identification Identification of sharyginite is only possible using advanced analytical methods, such as Raman spectroscopy or X-ray microanalysis (EDS/WDS), due to the microscopic size of the crystals. Preliminary identification under a microscope is based on observing dark brown, tabular crystals in a characteristic geological environment. ## Distinguishing from Similar Minerals Visually (under a microscope), it can be confused with other rare oxides of similar color and habit, such as other minerals from the brownmillerite group (e.g., srebrodolskite) or perovskite. Definitive differentiation requires chemical composition analysis, particularly checking for the presence and proportion of titanium and iron. ## Crystal Forms Sharyginite forms very small, tabular or lath-like crystals, reaching up to 20 µm in length and 5 µm in thickness. They occur as single lamellae or form irregular aggregates within the host rock.

Geological environment

## Genesis Sharyginite forms under conditions of high-temperature, low-pressure contact metamorphism (sanidinite facies). It forms as a result of reactions occurring in xenoliths of calc-silicate rocks that have been entrained and altered by hot magma. At its type locality in Germany, it occurs in limestone xenoliths within leucite-tephrite lavas. ## Mineral Associations This mineral coexists with other minerals typical of high-temperature environments, such as lakarnite, shulamitite, perovskite, magnesioferrite, fluorellestadite, cuspidine, harkerite, baghdadite, gehlenite, and srebrodolskite. ## Localities The most important and best-documented occurrence of sharyginite is its type locality – the Caspar quarry in Ettringen, in the volcanic Vordereifel region of Germany. Additionally, its presence has been confirmed in the Nabi Musa volcanic complex in the Palestinian Authority and in the Hatrurim Formation in Israel.

Rarity

Very rare

For collectors

## Quality Criteria The quality of sharyginite specimens is primarily assessed based on the abundance of microcrystals on the rock matrix and their association with other rare minerals. Since the crystals are microscopic, their individual form or "purity" are not typical criteria. The most desirable specimens are those from a well-defined type locality, with analytically confirmed mineral identity. ## Popular Localities The only source of specimens available on the collector's market is the type locality in Ettringen, Germany. Specimens from other confirmed localities practically do not appear in circulation.

Care and storage

## Cleaning Specimens containing sharyginite, which are usually micromounts, do not require cleaning. Any attempts at mechanical or chemical cleaning can irreversibly damage the delicate crystals. If necessary, dust can be removed very carefully using a photographic air blower or compressed air from a distance. ## What to Avoid Avoid contact with any chemicals, including acids and strong bases. Do not subject specimens to ultrasound. The mineral is stable, but it should be protected from mechanical damage and abrasion. ## Storage Specimens containing sharyginite should be stored exclusively in specialized micromount boxes that protect them from dust, shocks, and mechanical damage. Mineral identification is only possible under a microscope, so proper labeling is crucial.

External references

https://www.mindat.org/min-51845.html