Okhotskite
Chemical formula: Ca<sub>2</sub>Mn<sup>2+</sup>Mn<sup>3+</sup><sub>2</sub>(Si<sub>2</sub>O<sub>7</sub>)(SiO<sub>4</sub>)(OH)<sub>2</sub>·H<sub>2</sub>O
Ochockite is a rare, orange-red silicate from the pumpellyite group, valued by collectors for its intense color and attractive forms.
Properties
- Mohs hardness
- 6
- Luster
- Vitreous
- Streak
- Light brown
- Density
- 3.41
- Cleavage
- Good on {001}
- Fracture
- Uneven
- Transparency
- Translucent to opaque
- Crystal system
- Monoclinic
Diagnostic features
## Identification The most important diagnostic feature of ochockite is its unique, intense orange-red color combined with its characteristic form of occurrence – radial, fan-shaped, or spherulitic aggregates. Its rarity is also a clue. ## Distinguishing from Similar Minerals Ochockite can be confused with other minerals of similar color and form, such as inesite or rhodochrosite. It is distinguished from inesite by its harder structure and lack of perfect cleavage. Rhodochrosite, on the other hand, rarely forms radial aggregates, and more often occurs in rhombohedral forms or massive aggregates and reacts with acids. ## Crystal Forms Ochockite crystallizes in very small, bladed or tabular crystals, which almost always occur as aggregates. The most common forms are radial, fan-shaped, and spherulitic aggregates, forming rosettes or filling fissures and rock cavities.
Geological environment
## Genesis Ochockite is a low-temperature hydrothermal mineral. It forms in veins and fissures cutting manganese deposits, and in altered volcanic and sedimentary rocks rich in manganese. Its presence is associated with low-grade metamorphism processes. ## Mineral Associations This mineral often co-occurs with other manganese minerals. Its most common associations include: pyroxmangite, rhodochrosite, tephroite, spessartine, quartz, calcite, and other minerals from the pumpellyite group. ## Localities The most important and well-known occurrences of ochockite worldwide are the type locality in Japan (Wafuku mine, Kochi Prefecture) and the Kalahari manganese fields in the Republic of South Africa (N'Chwaning, Wessels mines). Specimens from South Africa are particularly valued for their size and quality.
Rarity
Rare
For collectors
## Quality Criteria The most highly prized ochockite specimens are characterized by an intense, vivid orange-red color without brownish hues. The form of the aggregates is also important – well-formed, complete rosettes and fans with sharp terminations are more desirable. Contrast with a light host rock (e.g., with calcite) and the absence of mechanical damage enhance its attractiveness. ## Popular Localities Specimens from the Kalahari manganese basin in South Africa are by far the most valued on the collector's market. Japanese specimens from the type locality are rarer in trade and are primarily of historical significance.
Care and storage
## Cleaning Ochockite specimens should be cleaned very carefully, using a soft brush to remove dust. If necessary, distilled water can be used, avoiding a strong stream. It should be dried quickly and thoroughly. ## What to Avoid This mineral is sensitive to strong acids, which can damage it. Ultrasonic cleaners and chemical cleaning should be avoided. It should not be heated or exposed to sudden temperature changes. ## Storage Collector's specimens of ochockite are best stored in closed boxes or display cases to protect them from dust and mechanical damage. It is stable under household conditions and does not require special humidity control or protection from light, although prolonged exposure to strong sunlight is inadvisable for most minerals.