Kerimasite

Chemical formula: Ca₃Zr₄+₂(Fe₃+₂Si)O₁₂

Kerimasite is a rare, dark brown to black garnet group mineral, related to schorlomite and kimzeyite.

## Characteristics Kerimasite is a mineral belonging to the garnet supergroup. It occurs as small, well-formed crystals, usually not exceeding 0.5 mm in size. Its crystals most often take the form of a rhombic dodecahedron. It is an opaque mineral with a dark brown to black color. ## Physical Properties Kerimasite is characterized by a Mohs hardness of approximately 7. It has a vitreous to resinous luster and a conchoidal fracture. The mineral's density is calculated at 4.14 g/cm³. ## History and Name The mineral's name comes from the Kerimasi volcano in Tanzania, where it was first discovered and described in 2009. This is its type locality. ## Uses Due to its rarity and small crystal size, kerimasite has no industrial application. It is solely an object of scientific interest and a collector's item for collectors of rare minerals and micromounts.

Properties

Mohs hardness: 7
Luster: Vitreous to resinous
Streak: White
Density: 4.14
Cleavage: None
Fracture: Conchoidal
Transparency: Opaque
Crystal system: Cubic

Diagnostic features

## Identification Identification of kerimasite requires advanced research methods, such as chemical analysis (EDS) and X-ray diffraction (XRD), due to its similarity to other garnets. Visually, it is characterized by its dark color and occurrence as small, well-formed crystals with the typical garnet shape. ## Distinguishing from Similar Minerals Kerimasite is difficult to distinguish from other dark garnets, such as schorlomite, andradite, or kimzeyite, without specialized analysis. It differs from them by subtle differences in chemical composition, especially the content of zirconium, iron, and silicon. ## Crystal Forms It forms idiomorphic (well-developed) crystals, typically in the form of a rhombic dodecahedron {110}, with sizes up to 0.5 mm.

Geological environment

## Genesis Kerimasite forms in metasomatic processes within carbonatites. In its type locality (Kerimasi volcano), it was found in lapilli and volcanic ash originating from carbonatite lavas. ## Mineral Associations This mineral co-occurs with calcite, phlogopite, magnetite, perovskite, apatite, and other minerals from the garnet group, such as kimzeyite and schorlomite. ## Localities The only confirmed occurrence of kerimasite in the world is its type locality - the Kerimasi volcano in the Arusha region of Tanzania.

Rarity

Very rare

For collectors

## Quality Criteria The most sought-after specimens by collectors are those with well-formed, sharp-edged crystals, clearly embedded on a contrasting rock matrix. Due to the microscopic nature of the mineral, the quality of the crystal itself, rather than its size, is crucial. Specimens rich in numerous, undamaged crystals are highly valued. ## Popular Localities The only source of kerimasite specimens is the Kerimasi volcano in Tanzania, which makes them highly sought after by collectors specializing in rare minerals and those from type localities.

Care and storage

## Cleaning It is recommended to clean only with compressed air to remove dust. Avoid ultrasonic cleaners and steam cleaning. ## What to Avoid Avoid contact with strong acids and chemicals. Despite its relatively high hardness, specimens should be protected from impacts and abrasion, which can damage small crystals. ## Storage Kerimasite specimens, due to their small size, are best stored in specialized micromount boxes that protect them from dust and mechanical damage.

Sources

IMA Mineral List (CNMNC)