Wroewolfeite

Chemical formula: Cu₂+₄S₆+O₄(OH)₆·₂H₂O

Wroewolfeite is a rare, hydrated copper hydroxide sulfate, forming characteristic emerald-green platy crystals and radiating aggregates.

## Characteristics Wroewolfeite is a sulfate mineral, chemically a hydrated copper hydroxide sulfate. Its most distinctive features are small, thin, platy or bladed crystals with a vivid, emerald-green to bluish-green color. These crystals often form fan-shaped, radiating, or stellate aggregates, as well as thin crusts on the host rock. Due to the small size of the crystals, the most beautiful specimens are usually observed under magnification. ## Physical Properties This mineral is very soft, with a Mohs hardness of only 2.5, meaning it can be scratched with a fingernail. It is also brittle. The luster of wroewolfeite is described as vitreous, and on planes of perfect cleavage, it can be pearly. It is transparent to translucent. Its density is approximately 3.28 g/cm³. ## Colors and Varieties The main and only color range of wroewolfeite is intense green, in shades from emerald to bluish-green. No color varieties or commercial varieties are distinguished. ## History and Name The mineral was first described in 1974 by Pete J. Dunn and Roland C. Rouse. The name "wroewolfeite" was given in honor of Dr. Caleb Wroe Wolfe (1908–1980), a professor of geology at Boston University, in recognition of his contributions to the fields of mineralogy and crystallography. ## Applications Wroewolfeite has no industrial applications. It is solely an object of interest for mineral collectors, especially those specializing in secondary copper minerals and micromounts.

Properties

Mohs hardness: 2.5
Luster: Vitreous to pearly
Streak: Light green
Density: 3.28
Cleavage: Perfect on {001}
Fracture: Uneven
Transparency: Transparent to translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Key diagnostic features of wroewolfeite include its emerald-green color, thin-platy crystal habit, perfect cleavage in one direction, and occurrence in radiating aggregates. Its paragenesis, i.e., co-occurrence with other secondary copper minerals, is also an important indicator. ## Distinguishing from Similar Minerals Wroewolfeite is a polymorph of langite and posnjakite, meaning it has the same chemical composition but a different crystal structure. Distinguishing it from these minerals without specialized tests (e.g., XRD) can be very difficult. It can also be confused with other green copper minerals: - **Langite**: Often forms slightly thicker crystals, but definitive distinction requires analysis. - **Posnjakite**: Usually occurs as finer, more granular coatings. - **Brochantite**: Forms acicular or prismatic crystals, not platy ones. - **Malachite**: Reacts vigorously with hydrochloric acid, releasing carbon dioxide bubbles, which wroewolfeite does not do. ## Crystal Forms Crystals are thin-platy, often elongated in one direction, resembling blades. They almost always occur in aggregates: fan-shaped, radiating, stellate, or in tangled masses. It also forms thin crusts and coatings.

Geological environment

## Genesis Wroewolfeite is a secondary mineral, forming in the oxidation zones (weathering) of copper ore deposits. It crystallizes from solutions rich in copper and sulfates under conditions of low temperature and pressure. It is often a relatively "young" geological mineral, forming contemporaneously in old mine workings (so-called post-mining mineral) on tunnel walls or roof beams. ## Mineral Associations It most commonly co-occurs with other secondary copper sulfates and carbonates, such as langite, posnjakite, brochantite, malachite, azurite, as well as with gypsum, chalcopyrite, and sphalerite. ## Localities This is a rare mineral, known from several dozen localities worldwide. The type locality, where it was discovered, is the Loudville Mine in Massachusetts, USA. Other significant occurrences include Ecton in England, Ľubietová (formerly Libethen) in Slovakia, mines in the Laurion region of Greece, and Tsumeb in Namibia.

Rarity

Rare

For collectors

## Quality Criteria The most highly valued wroewolfeite specimens are characterized by an intense, emerald color, well-formed, sharp crystals, and their large size (which for this mineral means crystals several millimeters long). Aesthetic, radiating aggregates on a contrasting rock matrix enhance their attractiveness. Association with other rare, colorful secondary minerals is also important. ## Popular Localities Specimens from historical localities in Ecton (Great Britain) and Ľubietová (Slovakia) are considered classic and most sought after by collectors. Material from the type locality in the USA is primarily of historical significance. Beautiful, microscopic specimens have also been found in Greece (Laurion).

Care and storage

## Cleaning Wroewolfeite specimens are very delicate and should be handled with care. To remove dust, it is best to use a soft brush or compressed air from a safe distance. Brief cleaning in distilled water is permissible, but the specimen should be thoroughly dried immediately. Ultrasonic cleaners should never be used. ## What to Avoid The mineral is very soft and susceptible to scratches and mechanical damage. Contact with acids and other aggressive chemicals should be avoided. As a hydrated mineral, it is sensitive to high temperatures, which can cause dehydration, leading to destruction and loss of color. ## Storage It is recommended to store wroewolfeite specimens in closed, padded boxes (e.g., "micromount" type) to protect them from dust, light, and mechanical damage. Due to its brittleness, it should not be stored in contact with harder minerals.

Sources

IMA Mineral List (CNMNC)