Béhierite
Chemical formula: TaBO<sub>4</sub>
Béhierite is an extremely rare tantalum borate, valued for its hardness and occurrence as small, sharp crystals in pegmatites in Madagascar.
Description
## Characteristics Béhierite is a tantalum borate, known for its exceptional rarity. It typically occurs as very small, but well-formed, sharp crystals. These take the form of tetragonal dipyramids, resembling miniature, octahedral diamonds. Specimens rarely exceed a few millimeters in size, and most are microminerals. ## Physical Properties This mineral is characterized by high hardness, ranging from 7 to 7.5 on the Mohs scale, making it scratch-resistant. Its most unusual feature is its very high density, reaching approximately 8 g/cm³, which is atypical for minerals with a non-metallic appearance. The luster is vitreous to adamantine, and the mineral itself can be transparent or translucent. ## Colors and Varieties Béhierite is most often colorless, pinkish, or pinkish-brown. No named color varieties or commercial varieties are distinguished. ## History and Name The mineral was described in 1961 by Mary E. Mrose and Harry J. Rose, Jr. The name honors Jean Béhier (1903–1965), a French mineralogist working for the Geological Survey of Madagascar, who first found this mineral and provided samples for study. ## Uses Due to its extreme rarity and small crystal size, béhierite has no industrial application. It is solely an object of interest for advanced mineral collectors and scientists.
Diagnostic features
## Identification The most important diagnostic feature of béhierite is its extremely high density, unusual for a mineral with a light color and vitreous luster. High hardness and the characteristic crystal form – sharp, tetragonal bipyramids – are also helpful. The context of its occurrence in granitic pegmatites from Madagascar is a key clue. ## Distinguishing from Similar Minerals Béhierite is sometimes confused with other small, hard minerals from pegmatites, such as **rhodizite** or **danburite**. Rhodizite crystallizes in the isometric system (dodecahedra, tetrahedra) and has a much lower density (approx. 3.4 g/cm³). Danburite is also much lighter (density approx. 3.0 g/cm³) and forms orthorhombic crystals. From **zircon**, it is distinguished by its chemical composition and usually lighter color. ## Crystal Forms This mineral forms almost exclusively simple, single crystals in the form of tetragonal bipyramids. It rarely forms intergrowths or aggregates.
Geological environment
## Genesis Béhierite is a pegmatitic mineral. It forms in the late stages of crystallization in rare-element-rich (lithium, tantalum, boron) granitic pegmatites, often within miarolitic cavities. ## Mineral Associations This mineral occurs in association with other pegmatitic minerals, such as tourmalines (liddicoatite, elbaite), pollucite, quartz, lepidolite, danburite, and rhodizite. ## Localities The only significant and confirmed locality for béhierite in the world is the Sahatany Valley region in Madagascar, especially the Manjaka pegmatite. Specimens from this locality constitute the global standard for this mineral.
Rarity
Extremely rare
Collector aspects
## Quality Criteria The collector appeal of béhierite is inextricably linked to its rarity. The most highly valued specimens are those with the largest possible (even if only 2-3 mm), sharp, and transparent crystals. An additional advantage is their attractive placement on the rock matrix, especially in association with color-contrasting minerals, such as colorful tourmalines. ## Popular Localities The pegmatites of the Sahatany Valley in Madagascar are considered the best and virtually only source of collector specimens. Practically all specimens available on the market originate from there.
Care and storage
## Cleaning Béhierite specimens, due to their small size and value, should be cleaned with the utmost care. The safest method is to use a soft brush to remove dust. If necessary, the specimen can be rinsed in distilled water. The use of ultrasonic cleaners is strongly discouraged. ## What to Avoid Avoid contact with strong chemicals, especially acids. Despite its high hardness, the mineral is brittle and sensitive to mechanical impact. Protect it from sudden temperature changes. ## Storage Béhierite, as a typical micromineral, should be stored in specialized "micromount" boxes that protect it from damage and loss. Exposure to strong sunlight is not recommended, although there is no evidence of fading.