Biehlite
Chemical formula: Sb<sup>3+</sup><sub>2</sub>Mo<sup>6+</sup>O<sub>6</sub>
Biehlite is a very rare antimony-molybdate, forming tiny, yellow crystals with a strong, adamantine luster.
Properties
- Mohs hardness
- 1-2
- Luster
- Adamantine
- Streak
- Light yellow
- Density
- 5.86
- Cleavage
- Perfect on {010}
- Fracture
- Uneven
- Transparency
- Transparent
- Crystal system
- Orthorhombic
Diagnostic features
## Identification Biehlite can be identified by its characteristic lemon-yellow color, very strong adamantine luster, and typical occurrence as tiny, tabular crystals forming radial aggregates. Its extreme softness is also a diagnostic feature, although difficult to verify without damaging the specimen. ## Distinguishing from Similar Minerals Due to its unique combination of features and extreme rarity, it is unlikely to be confused with other minerals. Within its type locality (Tsumeb), it might be mistaken for other secondary molybdenum or vanadium minerals, but its specific habit, luster, and chemical composition allow for unambiguous identification using analytical methods. ## Crystal Forms Crystals are very small, usually measuring up to 0.2 x 0.05 x 0.01 mm. They have a tabular or bladed habit, often flattened. They form characteristic, radial or stellar aggregates and rosettes on the surface of the host rock.
Geological environment
## Genesis Biehlite is a secondary mineral that formed in the oxidation zone (gossan) of the Tsumeb polymetallic deposit. It formed as a result of the weathering of primary antimony and molybdenum-bearing ores under strongly oxidized conditions. It occurs in vugs and fractures within heavily corroded tennantite ore. ## Mineral Associations This mineral occurs in association with other rare secondary minerals such as stibiconite, anglesite, quartz, and unidentified antimony oxides. It also co-occurs with relics of primary tennantite. ## Localities The only confirmed occurrence of biehlite in the world is its type locality – the Tsumeb mine in the Oshikoto region of Namibia. This is one of the most famous mineralogical sites globally, renowned for its immense diversity and perfectly formed crystals of rare minerals.
Rarity
Extremely rare
For collectors
## Quality Criteria The quality of a biehlite specimen primarily depends on the richness and aesthetics of the crystal aggregates. Samples with clearly formed, radial rosettes of intense yellow color, contrasting with the darker host rock, are most prized. The size of the crystals, although always microscopic, is also important – larger and better-formed needles increase the value of the specimen. The absence of damage to the delicate aggregates is also crucial. ## Popular Localities The only source of biehlite specimens is the historic Tsumeb mine in Namibia. All samples available on the collector's market originate from this single location and were collected before the mine's closure.
Care and storage
## Cleaning Biehlite specimens should be handled with the utmost care. Cleaning is highly inadvisable due to the extreme softness and fragility of the crystals. If absolutely necessary, compressed air can be used from a safe distance to remove loose dust particles. Any contact with water, chemicals, or tools should be avoided. ## What to Avoid Ultrasonic cleaners, chemical agents, acids, solvents, and water should be strictly avoided. The crystals are very soft (hardness 1-2 on the Mohs scale), flexible, but also brittle, so any mechanical pressure, rubbing, or bending should be avoided. It should be protected from high temperatures and humidity. ## Storage Biehlite specimens should be stored in stable conditions, in closed, padded "micromount" boxes to protect them from dust, mechanical damage, and humidity changes. It is not suitable for display outside of a specialized protective container.