Dolerophanite

Chemical formula: Cu²⁺₂OS⁶⁺O₄

Dolerophanite is a rare copper sulfate, forming tiny, tabular, reddish-brown crystals, found in volcanic exhalations.

## Characteristics Dolerophanite is a copper oxide sulfate, usually occurring as very small, tabular or bladed crystals. It also forms rosette aggregates, crusts, and earthy aggregates. Its name comes from Greek words meaning "deceptive" and "to appear," referring to its initial mistaken identification as another mineral. ## Physical Properties Dolerophanite crystals are brittle and exhibit a luster ranging from vitreous to resinous. The mineral is translucent to opaque. Its Mohs hardness is approximately 3, and its density ranges between 4.1 and 4.2 g/cm³. ## Colors and Varieties Dolerophanite has a characteristic brown to reddish-brown color, and in earthy aggregates, it can be lighter, yellowish-brown. No color varieties or commercial varieties are distinguished. ## History and Name The mineral was first described in 1873 by Arcangelo Scacchi based on samples from the fumaroles of Mount Vesuvius in Italy. The name, given by Scacchi, refers to the fact that he initially mistook it for chalcanthite, and its true nature proved to be "deceptive." ## Uses Dolerophanite has no industrial application. It is of purely scientific and collector's interest as a rare product of volcanic activity.

Properties

Mohs hardness: 3
Color: Dark brown, nearly black; yellow-brown in transmitted light.
Luster: Vitreous to resinous
Streak: Yellowish-brown
Density: 4.17
Cleavage: On <mi>{_101}</mi>, perfect.
Fracture: Uneven
Transparency: Translucent,Opaque
Crystal system: Monoclinic

Diagnostic features

## Identification Characteristic features of dolerophanite include its reddish-brown color, occurrence as small, tabular crystals, and its specific formation environment – volcanic fumaroles. It reacts with hydrochloric acid. ## Distinguishing from similar minerals Dolerophanite is sometimes confused with other rare copper sulfates from fumaroles, such as chalcochycanite (blue) or euchlorine. From chalcanthite, with which it was originally confused, it is distinguished by its color (chalcanthite is intensely blue) and significantly lower solubility in water. ## Crystal forms Crystals are usually very small, tabular or bladed, often flattened. They typically form radial aggregates, rosettes, or thin crusts on volcanic rocks.

Geological environment

## Genesis Dolerophanite is a secondary mineral, formed as a result of volcanic activity. It crystallizes directly from volcanic gases (exhalations) in high-temperature fumaroles or as a product of alteration of other copper minerals in such an environment. ## Mineral associations It most commonly co-occurs with other volcanic fumarole minerals, such as chalcanthite, chalcochycanite, tenorite, hematite, anglesite, and galenobismutite. ## Localities The most important and classic locality for dolerophanite is the fumaroles of Mount Vesuvius in Italy. It is also found in exhalative products of Mount Etna (Sicily), Tolbachik volcano in Kamchatka (Russia), and in the Laurion slag mine in Greece.

Rarity

Rare

For collectors

## Quality criteria The most prized dolerophanite specimens are those with well-formed, sharp crystals creating visually attractive rosettes or radial aggregates. Contrast with the light matrix rock and absence of mechanical damage are important. Due to the small size of the crystals, specimens visible to the naked eye are rare. ## Popular localities By far the most sought-after by collectors are classic specimens from Vesuvius in Italy. Rich crystallizations from Tolbachik volcano in Kamchatka are also highly valued.

Care and storage

## Cleaning Specimens should be cleaned only very carefully, using a soft brush to remove dust. Due to possible reactivity with water, wet cleaning should be avoided, and if absolutely necessary, only isopropyl alcohol should be used, and the specimen dried immediately. ## What to avoid Contact with water, acids, and other chemicals must be strictly avoided. The mineral is sensitive to moisture, which can lead to its slow decomposition. It should not be heated or exposed to sudden temperature changes. ## Storage Dolerophanite specimens should be stored in a dry place, preferably in a sealed, lockable display box with a desiccant (e.g., silica gel). They should be protected from dust and mechanical damage.

External references

https://www.mindat.org/min-1302.html