Zincovoltaite
Chemical formula: K₂Zn²⁺₅Fe³⁺₃Al(S⁶⁺O₄)₁₂·18H₂O
Zincovoltaite is a rare, hydrated sulfate of potassium, zinc, iron, and aluminum from the voltaite group, forming characteristic green-black crystals.
Properties
- Mohs hardness
- 3
- Luster
- Pitchy, Resinous, Vitreous
- Streak
- Grey-green
- Density
- 2.765
- Cleavage
- None
- Fracture
- Conchoidal
- Transparency
- Transparent,Translucent
- Crystal system
- Isometric
Diagnostic features
## Identification Characteristic features of zincovoltaite include its green-black or olive-green color, regular (isometric) crystal habit, and pitchy or resinous luster. A significant indicator is also its grayish-green streak. A key diagnostic feature is its solubility in water. ## Differentiation from Similar Minerals Zincovoltaite can be confused with other minerals from the voltaite group, such as voltaite itself. Differentiation requires advanced chemical analysis to determine the dominant cations (in this case, zinc). From other dark minerals with similar luster, it is distinguished by its lower hardness and solubility in water. ## Crystal Forms Zincovoltaite crystals crystallize in the isometric system and most often take the form of octahedra, sometimes in combination with a cube. It occurs as single, well-formed crystals.
Geological environment
## Genesis Zincovoltaite is a secondary mineral, forming in the oxidation zones of polymetallic ore deposits, especially those rich in zinc and iron. It forms under arid and desert conditions as a product of evaporation of sulfate solutions. ## Mineral Associations This mineral co-occurs with other secondary sulfates, such as melanterite, copiapite, voltaite, epsomite, goslarite, halotrichite, and also with pyrite. ## Localities The most important and type locality for zincovoltaite is the Xitieshan Mine in Haixi Prefecture, Qinghai Province, China. This is the only confirmed and well-documented locality for this mineral in the world.
Rarity
Very rare
For collectors
## Quality Criteria Most desired by collectors are specimens with well-formed, sharp-edged crystals exhibiting clear luster and high transparency. Crystals of significant size, embedded in a contrasting rock matrix, are highly valued. The purity of the specimen and the absence of mechanical damage are crucial for its value. ## Popular Localities The only source of collectible specimens is the type locality – the Xitieshan Mine in China. Specimens from this location are the standard by which all others are judged.
Care and storage
## Cleaning Zincovoltaite specimens should be cleaned with the utmost care, preferably using compressed air to remove dust. Contact with water is highly inadvisable, as the mineral is soluble in it. ## What to Avoid Absolutely avoid contact with water, water vapor, and any chemical agents. The mineral is sensitive to moisture and can be damaged or completely dissolved. It should also be protected from high temperatures and direct sunlight, which can lead to dehydration and structural changes. ## Storage Storage requires an environment with controlled, low humidity. It is best to place the specimen in a sealed, airtight container (a "perky box") along with a desiccant, such as silica gel. Display should be in enclosed showcases, away from heat and light sources.