Mathiasite
Chemical formula: (K,Ba,Sr)(Zr⁴⁺,Fe³⁺)(Mg,Fe³⁺)₂(Ti⁴⁺,Cr³⁺,Fe³⁺)₁₈O₃₈
Mathiasite is a rare, black, metallic oxide mineral of the crichtonite group, found in kimberlites.
Properties
- Mohs hardness
- 7.5
- Color
- Black
- Luster
- Metallic
- Streak
- Black
- Density
- 0
- Cleavage
- None
- Fracture
- Conchoidal
- Transparency
- Opaque
- Crystal system
- Trigonal
Diagnostic features
## Identification Mathiasite is identified by its black color, strong metallic luster, high hardness, and occurrence in a specific geological environment – kimberlites. It often occurs as rounded grains embedded in the rock. ## Distinguishing from Similar Minerals It can be confused with other black, metallic minerals found in kimberlites, such as ilmenite, magnetite, or chromite. Differentiation requires advanced analytical methods, such as chemical analysis (EDS/WDS), due to mathiasite's complex composition. Visually, it is difficult to identify unequivocally. ## Crystal Forms Most often, it forms rounded, irregular grains. Rarely, it is found as poorly formed, hexagonal, tabular crystals.
Geological environment
## Genesis Mathiasite is an igneous mineral, crystallizing under high pressure and temperature conditions deep within the Earth's mantle. It is a primary component of some kimberlites, which are rocks that are the main source of diamonds. ## Mineral Associations It coexists with other minerals typical of kimberlites, such as olivine, phlogopite, ilmenite, pyrope, diopside, and also with other rare minerals of the crichtonite group, such as lindsleyite. ## Localities The most important and type localities for this mineral are in the Republic of South Africa, in kimberlite mines such as Jagersfontein, Bultfontein, and Dutoitspan in the Kimberley region.
Rarity
Very rare
For collectors
## Quality Criteria The quality of a mathiasite specimen primarily depends on the size and degree of crystal development, which is extremely rare. The most valued are visible, distinct grains or crystals embedded in a contrasting kimberlite matrix. Due to its rarity, every documented specimen has scientific and collector's value. ## Popular Localities Almost all collector specimens come from historical kimberlite mines in the Republic of South Africa, especially from the Kimberley area.
Care and storage
## Cleaning It usually does not require cleaning. If necessary, a soft, dry brush can be used to remove dust. Avoid washing in water, especially if the specimen is embedded in a delicate rock matrix. ## What to Avoid Avoid contact with acids and strong chemical agents, which can damage the mineral's surface. Due to its occurrence in kimberlites, the entire rock matrix should be protected from moisture and sudden temperature changes. ## Storage Mathiasite specimens are best stored in stable conditions, in closed display boxes or cabinets, to protect them from dust and mechanical damage. It is recommended to store them away from direct sunlight and heat sources.