Radhakrishnaite
Chemical formula: PbTe₃(Cl,S)₂
Radhakrishnaite is an extremely rare lead telluride with chlorine and sulfur, forming tiny, metallic grains.
Properties
- Color
- Brownish gray
- Luster
- Metallic
- Streak
- Black
- Density
- 0
- Cleavage
- None
- Fracture
- Uneven
- Transparency
- Opaque
- Crystal system
- Tetragonal
Diagnostic features
## Identification Identification of radhakrishnaite is possible only with advanced laboratory techniques. In reflected light under a polarizing microscope, it is characterized by a creamy white color with a pinkish hue, distinct anisotropy (color change upon stage rotation), and a lack of internal reflections. Final confirmation requires chemical analysis (e.g., electron microprobe) to confirm the presence of lead, tellurium, chlorine, and sulfur. ## Distinguishing from Similar Minerals It can be confused with other microscopic tellurides, such as altaite (PbTe) or kostovite (AuCuTe₄). Differentiation is based on subtle differences in color in reflected light, anisotropy, and, most importantly, its unique chemical composition containing chlorine and sulfur. ## Crystal Forms This mineral occurs exclusively in the form of anhedral (irregular), irregular grains and aggregates, usually as inclusions in other minerals, most often in calaverite.
Geological environment
## Genesis Radhakrishnaite forms under hydrothermal conditions, in gold- and telluride-rich quartz veins. It is a late-stage crystallization mineral, forming at relatively low temperatures. ## Mineral Associations This mineral co-occurs with other tellurides and sulfides. It is most often accompanied by calaverite, petzite, hessite, altaite, pyrite, chalcopyrite, and native gold. It occurs as inclusions within calaverite or at its grain boundaries. ## Localities The only confirmed occurrence (type locality) is the Champion Gold Mine in Kolar Gold Fields, Karnataka state, India. This is the only known locality for this mineral worldwide.
Rarity
Extremely rare
For collectors
## Quality Criteria Due to its microscopic nature, radhakrishnaite is not evaluated based on typical collector criteria such as size or crystal form. The value of a specimen lies in the confirmed presence of this extremely rare mineral itself. The most valuable are polished sections with clearly visible under the microscope and well-documented analytically radhakrishnaite grains, in association with other rare tellurides.
Care and storage
## Cleaning Specimens containing radhakrishnaite, due to the microscopic size of the grains, practically do not require cleaning. Any attempts at mechanical or chemical cleaning of the host rock may destroy the delicate mineral inclusions. If necessary, dust can be removed with a gentle stream of compressed air. ## What to Avoid Avoid contact with any chemicals, acids, and ultrasonic cleaners. The mineral is likely sensitive to oxidation, so it should be protected from moisture and aggressive atmospheric agents. ## Storage Specimens should be stored under stable conditions, in closed containers or display cases, away from dust, moisture, and sudden temperature changes. It most often occurs in the form of polished sections, which are relatively durable, but should be protected from scratching.