Minohlite

Chemical formula: (Cu<sup>2+</sup>,Zn<sup>2+</sup>)<sub>7</sub>(S<sup>6+</sup>O<sub>4</sub>)<sub>2</sub>(OH)<sub>10</sub>·8H<sub>2</sub>O

Minohlite is a very rare, secondary copper and zinc sulfate, forming blue, spherical aggregates and crusts.

## Characteristics Minohlite is a hydrated copper and zinc sulfate. It occurs as spherical or hemispherical aggregates with a radial internal structure, as well as thin crusts and coatings. The individual crystals forming the aggregates are extremely small, acicular or bladed, which gives the surface of the aggregates a velvety or matte appearance. ## Physical properties Due to its microcrystalline nature, precise determination of the physical properties of individual crystals is difficult. The hardness is low, and the mineral is brittle. The luster of the aggregates is dull, earthy, or silky. It is an opaque mineral. ## Colors and varieties Minohlite has a characteristic, light blue or sky-blue color. No varieties are distinguished. ## History and name The mineral was approved by the IMA in 2013. Its name comes from its type locality – the Ohmi (Ōmi) mine in Niigata Prefecture, Japan, with the addition of the suffix "-lite" (from Greek "lithos" - stone). It was discovered by Japanese mineralogists and described in 2015. ## Uses Minohlite has no industrial application. It is solely an object of interest for collectors specializing in rare minerals and for scientists.

Properties

Mohs hardness
2
Luster
Vitreous
Streak
Light blue
Density
2.82
Cleavage
Perfect on {010}
Fracture
Uneven
Transparency
Translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Minohlite is identified by its characteristic mode of occurrence – spherical, radial aggregates – and its intense, light blue color. Its occurrence in the oxidation zones of copper and zinc ore deposits is also a key indicator. It reacts with acids. ## Distinguishing from similar minerals It can be confused with other secondary copper minerals of similar color and form, such as aurichalcite, rosasite, or chalcanthite. It is distinguished from aurichalcite and rosasite (carbonates) by its lack of reaction with cold hydrochloric acid (it does not effervesce). It is distinguished from chalcanthite (sulfate) by its mode of occurrence (chalcanthite forms crusts and stalactites, less often spherical aggregates) and lower solubility in water. ## Crystal forms It forms spherical or hemispherical aggregates up to several millimeters in diameter, composed of radially arranged, acicular or bladed crystals. It also occurs as thin crusts.

Geological environment

## Genesis It is a secondary mineral, formed in the oxidation (weathering) zones of polymetallic deposits rich in copper and zinc minerals. It forms as a result of sulfate-rich waters acting on primary ores. In its type locality, it formed on the walls of an adit in the mine. ## Mineral associations It co-occurs with other secondary minerals of the oxidation zone. In the Ohmi mine, it was found in association with gypsum, chalcanthite, goethite, sphalerite, and pyrite. ## Localities The only confirmed and described locality of minohlite in the world is its discovery site – the Ohmi (Ōmi) mine, Itoigawa City, Niigata Prefecture, Japan.

Rarity

Extremely rare

For collectors

## Quality criteria The most prized specimens are those with well-formed, spherical aggregates of intense blue color, contrasting with the rock matrix. The size of the aggregates and their quantity on the specimen significantly affect the value. The absence of mechanical damage to these delicate structures is also important. ## Popular localities The only source of specimens is the Ohmi mine in Japan, which makes them extremely desirable and difficult to acquire on the collector's market.

Care and storage

## Cleaning Minohlite specimens are extremely delicate and sensitive to water. Mechanical cleaning is highly risky. If necessary, a stream of compressed air can be used to remove loose dust. Any contact with water and other liquids should be avoided. ## What to avoid Contact with water, which can dissolve or damage the mineral, must be absolutely avoided. It should be protected from high temperatures, which can lead to dehydration and structural damage. Avoid vibrations and impacts due to its brittleness. ## Storage Specimens should be stored in closed, dry containers (e.g., "membrane boxes" or boxes with a desiccant). They should be displayed away from direct sunlight and heat sources, in stable humidity conditions.

Sources

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