Pinchite
Chemical formula: Hg²⁺₅O₄Cl₂
Pinchite is an extremely rare mercury oxychloride, forming microscopic, acicular crystals of an intense red color.
Properties
- Mohs hardness
- 2.5
- Color
- Dark brown, black
- Luster
- Adamantine
- Streak
- Red-brown
- Density
- 9.5
- Cleavage
- Good on {010}
- Fracture
- Uneven
- Transparency
- Transparent
- Crystal system
- Orthorhombic
Diagnostic features
## Identification Identification of pinchite is based on its characteristic features: intense red color, adamantine luster, and acicular crystal habit. The place of origin is also crucial – the vast majority of specimens come from the Terlingua district in Texas. Due to its microscopic size, final identification requires chemical analysis (EDS) or X-ray diffraction (XRD). ## Distinguishing from Similar Minerals Several other red mercury minerals found in the same locality can be confused with pinchite. The most similar is kleinite, which, however, crystallizes in the hexagonal system and often forms hexagonal prisms. Eglestonite has a similar composition but is yellow and darkens upon exposure to light. Cinnabar (HgS) has a similar color but usually forms more massive or granular aggregates and has a lower density. ## Crystal Forms Pinchite forms elongated, acicular or bladed crystals, often with pointed terminations. These crystals grow as chaotic aggregates, crusts, or radial clusters on calcite or directly on the host rock.
Geological environment
## Genesis Pinchite is a secondary mineral, forming in the oxidation zone of low-temperature, volcanic mercury deposits. It forms in voids and fissures in calcite-rich rocks, resulting from the reaction of hydrothermal solutions with earlier mercury minerals. ## Mineral Associations This mineral co-occurs with other rare mercury minerals characteristic of Terlingua-type localities. It is most commonly associated with: calcite, native mercury, cinnabar, eglestonite, kleinite, terlinguaite, montroydite, and gianellaite. ## Localities The most important and classic locality for pinchite is its type locality – the mines in the Terlingua district, Brewster County, Texas, USA. The vast majority of known specimens originate from there. Its occurrence has also been confirmed in the Khaidarkan mercury deposit in Kyrgyzstan.
Rarity
Extremely rare
For collectors
## Quality Criteria For pinchite collectors, the most important criteria are: the intensity and purity of the red color, the sharpness and definition of the crystals, and their size – although always microscopic, larger needles (above 0.5 mm) are more valued. The richness of the aggregate on the matrix and the aesthetic contrast with white calcite enhance its appeal. Association with other rare mercury minerals is also important. ## Popular Localities The only source of high-quality collectible specimens is the Terlingua district in Texas. Specimens from this locality are considered the global standard for this mineral.
Care and storage
## Cleaning Pinchite specimens are extremely delicate and small. Mechanical cleaning is inadvisable and almost always leads to crystal destruction. If absolutely necessary, dust can be attempted to be removed with a photographic air blower (non-contact). Water and any chemicals should be avoided. ## What to Avoid The mineral is very brittle and sensitive to vibrations and touch. Contact with acids and other chemicals should be avoided. As a mercury mineral, pinchite is toxic – avoid inhaling dust and wash hands after any contact. It does not require protection from light, but extreme temperatures should be avoided. ## Storage Pinchite specimens must be stored in specialized micromount boxes, which protect them from mechanical damage, dust, and vibrations. The box should be clearly labeled as containing a toxic mercury mineral.