Teallite
Chemical formula: PbSnS<sub>2</sub>
Teallite is a rare lead-tin sulfide, forming thin, flexible lamellae with a metallic luster, resembling graphite in appearance.
Properties
- Mohs hardness
- 1-2
- Luster
- Metallic
- Streak
- Black
- Density
- 6.36
- Cleavage
- Perfect on {001}
- Fracture
- Uneven
- Transparency
- Opaque
- Crystal system
- Orthorhombic
Diagnostic features
## Identification Key diagnostic features of teallite include its platy or scaly form, perfect cleavage in one direction, flexibility of the lamellae, and very low hardness (1-2 on the Mohs scale). The lead-gray color, strong metallic luster, and high density are also characteristic. The streak is black. ## Distinguishing from Similar Minerals Teallite is sometimes confused with graphite and molybdenite. It differs from graphite by its significantly higher density (graphite is very light) and a slightly brighter, more metallic luster. Molybdenite has a similar appearance and softness but usually has a more bluish-gray tint, whereas teallite is purely gray or black. Definitive differentiation often requires chemical analysis (EDS) to confirm the presence of lead and tin. ## Crystal Forms Teallite crystallizes in the orthorhombic system, but well-formed, single crystals are extremely rare. It typically occurs as aggregates composed of thin, tabular or scaly crystals, often arranged in rosettes or packets. The crystals are flexible (malleable).
Geological environment
## Genesis Teallite is a hydrothermal mineral, forming in ore veins under medium to high-temperature conditions. It is associated with intrusions of igneous rocks that provide the necessary elements, such as tin and lead. ## Mineral Associations It often co-occurs with other sulfides and sulfosalts. Typical associated minerals include pyrite, cassiterite, wurtzite, galena, sphalerite, stannite, franckeite, and cylindrite. The presence of these minerals, especially other tin minerals, is a good indicator during prospecting. ## Localities The most important and classic locality for teallite, from which the best specimens originate, is the Santa Cruz mine in Poopó, Oruro Department, Bolivia. Other known localities include the Carguaicollo mine, also in Bolivia. Outside Bolivia, its occurrence has been noted in small quantities in Japan (Ikuno mine, Hyōgo Prefecture), Argentina, and also in Nevada (USA).
Rarity
Rare
For collectors
## Quality Criteria The most prized teallite specimens are those consisting of large, well-formed, undamaged lamellae or rosettes. Aggregates with a strong, metallic luster, without signs of oxidation, are highly valued. Contrasting associations with other minerals, such as white quartz or shiny pyrite, significantly enhance the visual appeal and value of the specimen. ## Market Prices Teallite prices vary. Small, multi-centimeter specimens with typical lamellae can cost from several tens to several hundreds of dollars. Large, aesthetic aggregates with well-preserved crystals, especially from classic Bolivian localities, can fetch prices in the range of several thousand dollars on the collector's market. ## Popular Localities By far, the most sought-after specimens by collectors come from Bolivia, particularly from mines in the vicinity of Poopó in the Oruro Department. Specimens from these localities are considered the global standard for this mineral.
Care and storage
## Cleaning Teallite specimens are extremely delicate and soft. They should be cleaned only with a very soft brush, dry, to remove dust. The use of water is not recommended, as it can penetrate between the lamellae and cause them to delaminate or oxidize. ## What to Avoid Avoid contact with chemicals, especially acids, which can react with sulfides. The mineral is susceptible to mechanical damage – scratches, bending, and impacts. It should not be heated or subjected to ultrasound. Prolonged exposure to humid air can lead to slow oxidation and dulling of the surface. ## Storage Teallite specimens are best stored in closed, padded collector boxes to protect them from dust, moisture, and mechanical damage. Due to its softness, it should not be stored in contact with harder minerals.