Zincocopiapite

Chemical formula: Zn₂+Fe₃+₄(S₆+O₄)₆(OH)₂·₂₀H₂O

Zincocopiapite is a rare, hydrated zinc and iron sulfate, forming characteristic, bright yellow efflorescences and crusts.

## Characteristics Zincocopiapite is a mineral from the copiapite group, a hydrated zinc and iron sulfate. It most often occurs as microcrystalline crusts, efflorescences, and earthy aggregates. Less frequently, it forms small, tabular crystals gathered in scaly aggregates. Its most characteristic feature is its intense, canary-yellow or sulfur-yellow color. ## Physical properties This mineral is very soft, with a Mohs hardness of 2.5-3, meaning it can be scratched with a fingernail. It is light, with a density of about 2.19 g/cm³. It exhibits a pearly luster on cleavage planes and a vitreous luster on other surfaces. It is translucent. ## Colors and varieties Zincocopiapite occurs in shades of yellow, from canary yellow, through sulfur yellow, to greenish-yellow hues. No color varieties or trade names are distinguished. ## History and name The mineral's name refers to its chemical composition – the dominance of zinc and its connection to the structural pattern of the group, copiapite. Copiapite, in turn, took its name from its occurrence near the city of Copiapó in Chile. Zincocopiapite was recognized as a distinct mineral species in 1957.

Properties

Mohs hardness: 2.5-3
Luster: Pearly
Streak: Pale yellow
Density: 2.19
Cleavage: Perfect on {010}
Fracture: Uneven
Transparency: Translucent
Crystal system: Triclinic

Diagnostic features

## Identification Features facilitating the identification of zincocopiapite include its bright yellow color, occurrence as efflorescences and brittle crusts, and pearly luster. The geological context is also crucial – oxidation zones of sulfide deposits, especially zinc and iron. ## Distinguishing from similar minerals Zincocopiapite is visually indistinguishable from other minerals of the copiapite group without advanced chemical analyses (e.g., EDS) confirming the dominance of zinc. It can be confused with native sulfur, which, however, has a resinous luster and often a different genesis. Jarosite can be similar in color but usually has a more earthy or dull appearance. ## Crystal forms Zincocopiapite crystals are extremely rare and appear as thin, hexagonal tablets. Usually, this mineral forms microcrystalline, scaly, or bladed aggregates, and is most commonly found as powdery efflorescences and brittle crusts.

Geological environment

## Genesis It is a secondary mineral, formed as a result of weathering and oxidation of sulfide minerals, mainly sphalerite (zinc sulfide) and pyrite or marcasite (iron sulfides). It forms under strongly acidic conditions, in dry or semi-arid climates, often as efflorescences on the walls of old mine workings. ## Mineral associations Zincocopiapite often co-occurs with other secondary sulfates, such as copiapite, melanterite, fibroferrite, rhomboclase, voltaite, and also with gypsum. In its vicinity, one can also find the primary sulfides from which it formed, namely sphalerite and pyrite. ## Localities Important localities worldwide include the Rammelsberg mine in Goslar (Germany), known for well-formed specimens, and Vulcano Island (Italy), which is the type locality. It also occurs in old mines in the Atacama Desert in Chile, in Bolivia, and in some regions of the USA (e.g., Utah).

Rarity

Rare

For collectors

## Quality criteria The most prized zincocopiapite specimens are those that form rich, intensely colored crusts on a small rock matrix. Rare, macroscopic microcrystals are exceptionally sought after. The attractiveness of a specimen is also enhanced by co-occurrence with other rare, colorful secondary sulfates. ## Popular localities The historic Rammelsberg mine in Germany is considered classic and provides the best specimens. Good quality material also comes from some dry regions of Chile and Bolivia.

Care and storage

## Cleaning Zincocopiapite specimens are extremely sensitive to water, in which they readily dissolve. Only dry methods should be used for cleaning: a soft brush to remove dust or gentle blowing with compressed air from a safe distance. ## What to avoid Contact with water and other liquids must be absolutely avoided. The mineral is also sensitive to changes in humidity – in overly dry air, it can dehydrate and crumble. It should be protected from high temperatures, direct sunlight, and mechanical damage due to its low hardness. ## Storage It is recommended to store specimens in tightly sealed, transparent containers (e.g., "membrane boxes" or boxes with gaskets), which help maintain a stable humidity level. Protect from dust and shocks.

Sources

IMA Mineral List (CNMNC)