Langhofite
Chemical formula: Pb²⁺₂(OH)[W⁶⁺O₄(OH)]
Langhofite is a very rare, secondary lead tungstate mineral, forming microscopic, colorless to white tabular crystals.
Properties
- Mohs hardness
- 2.5
- Color
- colourless to white
- Luster
- Vitreous, Pearly
- Streak
- white
- Density
- 7.95
- Cleavage
- {010} and {100} cleavages
- Fracture
- Irregular/Uneven,Splintery
- Transparency
- Transparent
- Crystal system
- Triclinic
Diagnostic features
## Identification Identification of langhofite is possible only through advanced analytical methods, such as Raman spectroscopy or X-ray diffraction (XRD), due to its microscopic size and occurrence. Visually, it is characterized by tiny, colorless, tabular crystals forming rosette-like aggregates on the matrix rock. ## Distinguishing from Similar Minerals It can be confused with other secondary, colorless lead or tungsten minerals, such as hydrocerussite, raspberrite, or stolzite, which may co-occur in the same environment. Reliable differentiation from these minerals requires specialized chemical and structural analysis. ## Crystal Forms Crystals are very small, thin, and tabular, with a hexagonal outline. They often form radial or rosette-like clusters and aggregates.
Geological environment
## Genesis Langhofite is a secondary mineral, formed in the oxidation zones of polymetallic deposits. In its type locality (Clara Mine), it forms as a result of the weathering of tungsten minerals (mainly scheelite) in the presence of lead-rich solutions, originating from the oxidation of galena. ## Mineral Associations This mineral co-occurs with other secondary lead and tungsten minerals. In the Clara Mine, it was found in association with cerussite, mimetite, stolzite, raspberrite, as well as quartz and barite. ## Localities The only confirmed locality of langhofite in the world is the dumps of the Clara Mine, Rankach, Oberwolfach, Black Forest, Baden-Württemberg, Germany. This is its type locality.
Rarity
Extremely rare
For collectors
## Quality Criteria As a microscopic mineral, langhofite is primarily valued for its confirmed presence on a specimen. The most highly rated specimens are those where well-formed, though still microscopic, rosette-like crystal aggregates are visible, clearly standing out from the matrix rock. The abundance of these aggregates on the matrix and association with other rare secondary minerals increase the collecting and scientific value of the specimen.
Care and storage
## Cleaning Specimens with langhofite should be handled with utmost care due to their extreme rarity and microscopic size. Cleaning is not recommended, as mechanical methods (brushes, ultrasonics) will irreversibly damage the delicate crystals. Dust can only be removed using a gentle stream of compressed air. ## What to Avoid Avoid contact with all chemicals, including acids and bases, which may react with the mineral. Also avoid ultrasonic cleaners, high temperatures, and sudden changes in pressure. ## Storage Specimens should be stored under stable conditions in sealed "micromount" containers to protect them from dust, mechanical damage, and contamination. Due to the lead content, it is recommended to wash hands after contact with the specimen.