Zincmelanterite
Chemical formula: Zn<sup>2+</sup>S<sup>6+</sup>O<sub>4</sub>·7H<sub>2</sub>O
Zinc-melanterite is a hydrated zinc sulfate, a zinc analog of melanterite, occurring as efflorescences and crusts.
Properties
- Mohs hardness
- 2
- Luster
- Vitreous
- Streak
- White
- Density
- 2.02
- Cleavage
- Perfect on {001}
- Fracture
- Conchoidal
- Transparency
- Transparent to Translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Zinc-melanterite is most easily identified by its occurrence as greenish, secondary efflorescences and crusts in the oxidation zones of zinc-bearing deposits. A key diagnostic feature is its solubility in water and its astringent, metallic taste (although taste testing is highly discouraged). The green color combined with its instability and genesis is a strong indicator. ## Distinguishing from Similar Minerals - **Melanterite**: This is the iron analog. It usually has a more intense, green or bluish-green color. Definitive differentiation requires chemical analysis to confirm the dominance of zinc over iron. - **Goslarite**: This is pure zinc sulfate, usually colorless or white. Zinc-melanterite owes its green color to iron admixture, which distinguishes it from typical goslarite. - **Pisanite**: This is a copper variety of melanterite, usually blue to bluish-green. ## Crystal Forms It most often forms efflorescences, coatings, crusts, and earthy masses. It also occurs in the form of fibrous or hair-like aggregates and small stalactites. Well-formed, short prismatic or tabular crystals are extremely rare.
Geological environment
## Genesis Zinc-melanterite is a secondary mineral, formed by the weathering (oxidation) of sulfide zinc ores, mainly sphalerite, in a humid environment. It forms as an unstable product in mines, dumps, and natural oxidation zones of ore deposits. Its formation is often a contemporary process, observed in active or abandoned mining workings. ## Mineral Associations This mineral co-occurs with other secondary sulfates and minerals of the oxidation zone. It is most often accompanied by: melanterite, goslarite, epsomite, chalcanthite, gypsum, as well as sphalerite (as a primary mineral), pyrite, and galena. ## Localities Zinc-melanterite is a rare mineral, found in many places around the world, but usually in small quantities. Key localities include: - **USA**: Vulcan Mine, Gunnison County, Colorado (type locality); mines in the Leadville district, Colorado; mine in Butte, Montana. - **Germany**: Rammelsberg Mine in the Harz Mountains. - **Poland**: Occurs in trace amounts in old workings of zinc and lead ore mines in the Silesian-Kraków region (e.g., in Olkusz). - **Greece**: Mines in the Lavrion region. - **Japan**: Yoshino Mine, Yamagata Prefecture.
Rarity
Rare
For collectors
## Quality Criteria The collector appeal of zinc-melanterite is specific and aimed at specialized collectors. Specimens with well-formed, even small, crystals are most valued, which is extremely rare. Impressive speleothems, such as small stalactites, are also highly rated, provided they are stable. The intensity and shade of the green color also affect aesthetic value. Due to the mineral's instability, it is crucial that the specimen is well-preserved and properly secured. ## Popular Localities Although this mineral occurs in many places, collectible specimens come from only a few. Historically, classic samples came from the Vulcan Mine in Colorado (USA). Currently, interesting specimens, especially in the form of small stalactites, are found in the mines of the Lavrion region in Greece.
Care and storage
## Cleaning Zinc-melanterite is very sensitive and soluble in water, so **it must not be wet cleaned**. Any contact with water, even a damp cloth, will cause damage or complete dissolution. Dust can be removed very carefully using a soft brush or a stream of dry air from a short distance. ## What to Avoid Contact with water and any moisture must be strictly avoided. The mineral is unstable in dry air – it loses water and can crumble into a white powder (efflorescence). Conversely, in overly humid air, it can absorb water and deliquesce. It should be protected from temperature changes and direct sunlight. ## Storage Zinc-melanterite specimens require storage under special conditions. The best solution is a sealed, transparent container (e.g., a "perky box") that will provide a stable microclimate and protect the mineral from humidity fluctuations and mechanical damage. A humidity-regulating agent can be placed inside the container to prevent both drying out and excessive moisture.