Stibiotantalite

Chemical formula: Sb³⁺Ta⁵⁺O₄

Stibiotantalite is a rare antimony and tantalum oxide, valued by collectors for its well-formed crystals with a characteristic resinous luster.

## Characteristics Stibiotantalite is a mineral from the cernantite group, an oxide of antimony and tantalum. It forms tabular or short-prismatic crystals, often with a square or rectangular outline. Specimens are sometimes partially or completely pseudomorphs after tantalite and microlite. Its surface often exhibits characteristic striations. ## Physical Properties This mineral is characterized by a hardness of 5.5 on the Mohs scale and a significant density of approximately 5.98 g/cm³. The luster is strong, described as resinous to submetallic. It is translucent, rarely transparent. It exhibits weak piezoelectric properties. ## Colors and Varieties Stibiotantalite occurs in various shades of brown and yellow – from dark brown, through reddish-brown and reddish-yellow, to light yellowish-brown and greenish-yellow. No named varieties are distinguished, and color variability depends on impurities and crystallization conditions. ## History and Name The mineral's name, given in 1893, directly refers to its chemical composition – the presence of antimony (Latin: *stibium*) and tantalum. It was discovered in tin-bearing alluvium in Greenbushes, Western Australia, which is its type locality. ## Uses Due to its rarity, stibiotantalite has no industrial applications. It is solely an object of interest for collectors and scientists studying granitic pegmatites.

Properties

Mohs hardness: 5.5
Luster: Resinous
Streak: Light yellow, yellow-brown
Density: 5.98
Cleavage: {001} distinct; {100} indistinct.
Fracture: Sub-Conchoidal
Transparency: Translucent
Crystal system: Orthorhombic

Diagnostic features

## Identification Stibiotantalite can be identified by its characteristic, strong resinous luster, high density (it is noticeably heavy for its size), tabular crystal habit, and yellowish-brown streak. It often occurs as pseudomorphs. ## Distinguishing from Similar Minerals It can be confused with other tantalum and niobium minerals, such as tantalite-(Mn) or columbite. It is distinguished by its lighter, yellowish streak (compared to the darker streak of columbite/tantalite), lower hardness, and characteristic resinous luster, in contrast to the often metallic luster of columbites. ## Crystal Forms Crystals are usually tabular, flattened along one axis, or short-prismatic. They often form twins, and striations are visible on their faces. It also occurs in granular aggregates and as pseudomorphs after other minerals.

Geological environment

## Genesis Stibiotantalite is a mineral of magmatic origin, crystallizing in the late stages of the evolution of granitic pegmatites, especially those rich in lithium and phosphates (LCT type - lithium, cesium, tantalum). ## Mineral Associations It often co-occurs with minerals such as quartz, albite, microcline, muscovite, lepidolite, spodumene, tantalite-(Mn), microlite, cassiterite, and beryl. ## Localities The most important localities worldwide include the historical type locality in Greenbushes, Western Australia. Significant specimens also come from pegmatites in Afghanistan (near Jalalabad), Pakistan (Shigar Valley), USA (California - including the Himalaya and Little Three mines), Brazil (Minas Gerais), and Mozambique (Muiane mine).

Rarity

Rare

For collectors

## Quality Criteria The most prized specimens by collectors are those with sharply terminated, well-formed crystals with smooth, lustrous faces. Transparent crystals with an intense, honey-yellow or reddish-brown color are highly valued. The attractiveness is also enhanced by the crystal's placement on a contrasting rock matrix, e.g., on white albite. ## Popular Localities Specimens from pegmatites in Afghanistan and Pakistan are considered among the best in the world, providing large, often partially gem-quality crystals. Classic, though less frequently available, are specimens from California (USA) and Western Australia.

Care and storage

## Cleaning Stibiotantalite specimens should be cleaned very carefully, using a soft brush to remove dust. If necessary, distilled water can be used, followed by thorough drying of the specimen with a soft cloth or compressed air. ## What to Avoid Avoid contact with acids and strong chemical agents, which can damage the mineral's surface. It should not be heated or subjected to ultrasound. Although relatively hard, it is brittle and sensitive to impact. ## Storage Collector specimens of stibiotantalite are best stored in separate, padded boxes to prevent scratches and contact with harder minerals. They should be protected from dust and moisture.