Majindeite

Chemical formula: Mg₂Mo₄+₃O₈

Majindeite is an extremely rare, black magnesium molybdenum oxide, forming tiny, octahedral crystals.

## Characteristics Majindeite is a very rare mineral from the oxide group, chemically classified as a magnesium molybdenum oxide. It occurs as very small, well-formed, octahedral crystals, whose size does not exceed 0.2 mm. Its crystals are isometric and have a metallic luster. ## Physical Properties Majindeite crystals are opaque and brittle. The Mohs hardness is estimated at approximately 6. This mineral is characterized by a high density of 5.56 g/cm³ (calculated). ## Colors and Varieties Majindeite has a black color and a black streak. No varieties are known. ## History and Name The mineral was named in honor of Majinde Chai (1920-1991), Director General of the Department of Mineral Resources of Thailand, in recognition of his contribution to the country's geology. It was discovered in the KAO diamond mine, Kimberlite pipe, Butha-Buthe in Lesotho and approved as a new mineral species by the IMA in 1992. ## Uses Due to its extreme rarity and microscopic crystal size, majindeite has no industrial application. It is solely an object of scientific interest and a collector's item for specialized micromineral collectors.

Properties

Mohs hardness: 6
Luster: Metallic
Streak: Black
Density: 5.56
Cleavage: None
Fracture: Uneven
Transparency: Opaque
Crystal system: Cubic

Diagnostic features

## Identification Identification of majindeite is practically only possible using advanced analytical methods, such as chemical analysis (EDS) and X-ray diffraction (XRD), due to its microscopic size. Visually, it can be identified under a microscope as very small, black, metallic-lustered octahedra. ## Differentiation from Similar Minerals It can be confused with other black, metallic minerals found in kimberlites, such as magnetite, chromite, or ilmenite. Differentiation requires specialized equipment – majindeite is distinguished by its unique chemical composition (presence of molybdenum and magnesium) and regular crystallographic system. ## Crystal Forms Majindeite forms exclusively small, single crystals with an octahedral habit, reaching up to 0.2 mm in size.

Geological environment

## Genesis Majindeite is a mineral of magmatic origin. It forms as a primary phase in ultramafic igneous rocks – kimberlites. Its presence is associated with processes occurring deep within the Earth's mantle, under conditions of high pressure and temperature. ## Mineral Associations This mineral co-occurs with other minerals typical of kimberlites, such as diamond, ilmenite, pyrope, diopside, forsterite, enstatite, phlogopite, and perovskite. ## Localities The only confirmed occurrence of majindeite in the world is its type locality: the KAO kimberlite pipe in the Butha-Buthe district of Lesotho.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a majindeite specimen is primarily assessed based on the size and degree of crystal development, which is rare. The most desirable specimens are those with sharp, lustrous, undamaged octahedra, clearly set on a contrasting rock matrix. Due to the microscopic nature of the mineral, the ability to observe it under magnification is crucial. ## Popular Localities The only known source of specimens is the KAO diamond mine in Lesotho. Material from this locality is extremely difficult to obtain.

Care and storage

## Cleaning Specimens containing majindeite, due to the microscopic size of the crystals, generally do not require cleaning. If necessary, compressed air (from a safe distance) can be used to remove dust. Avoid contact with water and any chemicals. ## What to Avoid Avoid ultrasonic cleaners, chemical agents, acids, and high temperatures. The crystals are very small and brittle, so they should be protected from any impact or abrasion. ## Storage Specimens should be stored in specialized micromineral boxes (so-called micromounts) that protect them from dust, moisture, and mechanical damage. Avoid exposure to direct sunlight, although there is no evidence of fading.

Sources

IMA Mineral List (CNMNC)