Zincobotryogen
Chemical formula: Zn<sup>2+</sup>Fe<sup>3+</sup>(S<sup>6+</sup>O<sub>4</sub>)<sub>2</sub>(OH)·7H<sub>2</sub>O
A zinc-rich variety of botryogen, a rare hydrated zinc and iron sulfate, forming characteristic spherical crystal aggregates.
Properties
- Mohs hardness
- 2-2.5
- Luster
- Vitreous
- Streak
- Pale yellow
- Density
- 2.13
- Cleavage
- Perfect on {010}
- Fracture
- Conchoidal
- Transparency
- Transparent to Translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Zincobotryogen is most easily recognized by its characteristic mode of occurrence – radial or spherical aggregates of an intense yellow to orange color. It forms encrustations on other minerals in oxidation zones. Its low hardness and water solubility are key diagnostic features. ## Distinguishing from Similar Minerals It can be confused with other secondary iron sulfates, such as botryogen, copiapite, or butlerite. It is distinguished from botryogen by the presence of zinc, which requires chemical analysis (EDS). Visually distinguishing it from other yellow sulfates can be impossible without advanced studies. Butlerite and copiapite often have more greenish hues. ## Crystal Forms Crystals are prismatic and elongated, almost acicular, but rarely occur in isolated form. They almost always form dense, radial aggregates, spherical clusters (spherulites), as well as encrustations and coatings.
Geological environment
## Genesis Zincobotryogen is a secondary mineral, formed as a result of weathering and oxidation of sulfide deposits, especially those rich in pyrite (FeS₂) and sphalerite (ZnS). It forms under dry and acidic conditions, often as a product of mine fires or evaporation of mine waters. ## Mineral Associations It often co-occurs with other sulfates, such as botryogen, copiapite, butlerite, voltaite, melanterite, epsomite, as well as with gypsum and native sulfur. ## Localities The most important localities, from which well-formed specimens originate, include the United Verde mine in Jerome, Arizona (USA), where it was first described. It is also found in the Rammelsberg mines in the Harz Mountains (Germany) and in other dry, weathering mining environments worldwide.
Rarity
Very rare
For collectors
## Quality Criteria Specimens with well-formed, spherical aggregates of intense, orange color are most valued by collectors. Contrast with the rock matrix and the absence of damage to delicate structures are important. Large encrustations covering a significant area of the host rock are also sought after. ## Popular Localities Classic and most desirable specimens come from the type locality – the United Verde mine in Jerome, Arizona, USA. Specimens from this location are considered exemplary for this mineral.
Care and storage
## Cleaning Zincobotryogen specimens are very delicate and water-soluble. They should be cleaned only dry, using a soft brush or compressed air from a safe distance to remove dust. Any contact with water, even a damp cloth, can damage or completely dissolve the mineral. ## What to Avoid Water, acids, detergents, and other chemicals must be absolutely avoided. The mineral is sensitive to high air humidity, which can lead to its slow degradation. It should also be protected from high temperatures and direct sunlight, which can cause fading and dehydration. ## Storage It is recommended to store specimens in a dry place, preferably in closed, airtight containers or display cases away from sources of moisture. Using silica gel packets (desiccant) inside the container is a good solution. Due to its fragility, avoid placing other specimens on top of it.