Jôkokuite
Chemical formula: Mn<sup>2+</sup>S<sup>6+</sup>O<sub>4</sub>·5H<sub>2</sub>O
Jôkokuite is a hydrated manganese sulfate, forming pale pink, prismatic crystals and crusty coatings.
Properties
- Mohs hardness
- 2.5
- Luster
- Vitreous
- Streak
- White
- Density
- 2.03
- Cleavage
- Perfect on {1-10}
- Fracture
- Conchoidal
- Transparency
- Transparent to translucent
- Crystal system
- Triclinic
Diagnostic features
## Identification Key diagnostic features of jôkokuite include its pale pink color, occurrence as small, prismatic crystals or coatings, and water solubility. Reaction to moisture is one of the simplest tests, though destructive. This mineral is also unstable in dry air, where it can dehydrate. ## Distinguishing from Similar Minerals Jôkokuite can be confused with other pink, secondary sulfates. Distinguishing it from similar minerals, such as bieberite (cobalt sulfate), requires advanced chemical analyses (EDS, XRD), as their physical properties and appearance can be similar. Confirming the dominance of manganese in its composition is crucial. ## Crystal Forms Jôkokuite crystals are prismatic, elongated, and often sharply terminated. They typically form small, radial or acicular aggregates. They also occur as thin crusts and coatings on rocks.
Geological environment
## Genesis Jôkokuite is a secondary mineral, formed in the oxidation zones of manganese ore deposits. It forms as a result of the weathering of primary minerals, such as rhodochrosite, under low humidity conditions, most often in mine workings. It is a product of post-mining activity. ## Mineral Associations At the type locality, jôkokuite is associated with minerals such as ilesite, rosenite, melanterite, gypsum, rhodochrosite, and native sulfur. ## Localities The only confirmed and described occurrence of jôkokuite in the world is its type locality - the Jôkoku mine on the Oshima Peninsula, Hokkaido Prefecture, Japan.
Rarity
Extremely rare
For collectors
## Quality Criteria The most valued jôkokuite specimens are those with well-formed, sharp prismatic crystals, forming attractive, radial aggregates. An intense, pale pink color and contrast with the rock matrix are important. Due to its extreme rarity, any specimen with visible crystals is considered valuable. ## Popular Localities The only source of jôkokuite specimens is its type locality - the Jôkoku mine in Japan. Material from this locality is extremely difficult to obtain and very rarely appears on the collector's market.
Care and storage
## Cleaning Jôkokuite is water-soluble, so it must absolutely not be cleaned with water. Only a soft brush or compressed air from a safe distance should be used to remove dust. ## What to Avoid Avoid contact with water, water vapor, and all liquids. The mineral is very sensitive to moisture and can completely dissolve. It should be protected from high temperatures, which can cause the loss of water from its structure (dehydration) and damage the specimen. ## Storage Jôkokuite specimens must be stored in sealed, dry containers, preferably with a desiccant (e.g., silica gel). They should be displayed away from direct sunlight and heat sources, in stable temperature conditions.