Kafehydrocyanite
Chemical formula: K₄[Fe(CN)₆]·H₂O
Kafehydrocyanite is a rare organic mineral, a hydrated potassium hexacyanoferrate, found as fine, yellowish crystals and coatings.
Properties
- Mohs hardness
- 2-2.5
- Luster
- Vitreous
- Streak
- White
- Density
- 0
- Transparency
- Transparent to translucent
- Crystal system
- Tetragonal
Diagnostic features
## Identification Key diagnostic features include very low hardness (2-2.5), characteristic yellowish or greenish colors, tabular habit of small crystals, and occurrence as coatings. Reaction to water (solubility) is also a characteristic feature, though destructive to the sample. Final identification requires advanced analytical methods, such as X-ray diffraction (XRD). ## Distinguishing from Similar Minerals It can be confused with other secondary minerals of similar colors, such as native sulfur (different crystal habit, characteristic smell when rubbed) or some zeolites. However, kafehydrocyanite is distinguished by its extreme softness and specific environment of occurrence. ## Crystal Forms It forms very small, thin, tabular crystals with a square or rectangular outline. It also occurs as granular aggregates, powdery coatings, and efflorescences on the surface of other minerals or rocks.
Geological environment
## Genesis This is a secondary mineral, likely of anthropogenic origin. It forms in the oxidation zones of gold deposits where mining operations used cyanidation processes for gold extraction. It results from the reaction of cyanide solutions with iron minerals under low-temperature conditions. ## Mineral Associations It co-occurs with minerals typical of gold deposit oxidation zones, such as quartz, calcite, pyrite, chalcopyrite, and other secondary iron minerals. ## Localities The most important and type locality is the Medvezhii Log gold deposit in the Olkhovskoye area, Tuva Republic, Russia. This is the only confirmed and well-documented locality for this mineral worldwide.
Rarity
Very rare
For collectors
## Quality Criteria Specimens with well-formed, even microscopic, crystals of intense yellow or yellowish-green color are most desired by collectors. Rich coatings covering a significant area of the matrix rock are also highly valued. Due to the microscopic size of the crystals, specimens are usually evaluated under magnification. ## Popular Localities The only source of collectible specimens is the type locality – the Medvezhii Log deposit in Russia. Material from this location is extremely difficult to acquire on the market.
Care and storage
## Cleaning Kafehydrocyanite specimens are extremely delicate and sensitive to water. Cleaning should be limited to an absolute minimum. Only very careful removal of dust with a soft brush or a stream of compressed air from a distance is permissible. ## What to Avoid Contact with water, which can dissolve or damage the mineral, must be absolutely avoided. The use of any chemical agents, ultrasonic cleaners, and exposure of the specimen to high temperatures and sudden changes in temperature are also inadvisable. Due to potential light sensitivity, prolonged exposure to direct sunlight should be avoided. ## Storage Kafehydrocyanite requires storage in stable, dry conditions. It is best kept in a closed, airtight "micromount" box or in a display cabinet away from sources of moisture and dust. Due to its softness, contact with harder minerals should be avoided.