Ilesite

Chemical formula: Mn²⁺S⁶⁺O₄·4H₂O

Ilesite is a rare, water-soluble hydrated manganese sulfate, forming ephemeral, pale pink or greenish coatings and efflorescences.

## Characteristics Ilesite is a mineral from the sulfate group, chemically a hydrated manganese sulfate. It occurs extremely rarely, forming ephemeral coatings, crusts, efflorescences, and occasionally small, prismatic crystals. It is usually colorless, white, with greenish or pale pink hues, which depend on iron and manganese impurities. Due to its water solubility, it is an ephemeral mineral that easily degrades in a humid environment. ## Physical Properties Ilesite is very soft, with a Mohs hardness of approximately 2-3. It has a vitreous luster and is transparent to translucent. Its density is low, around 2.1 g/cm³. This mineral is brittle and has perfect cleavage in one direction. ## Colors and Varieties The most common colors are white, colorless, greenish, or pale pink. The hue depends on the proportion of manganese (Mn²⁺) ions and often accompanying iron (Fe²⁺), which can substitute for each other in the crystal structure. No named varieties of this mineral are distinguished. ## History and Name The mineral's name comes from Malvern Wells Iles (1852-1890), an American chemist and metallurgist, who first described this substance at the Hall Valley Mine in Colorado, USA. The mineral was described in 1881. ## Uses Ilesite has no industrial applications. It is solely of interest to collectors specializing in rare minerals and scientists studying the weathering processes of ore deposits.

Properties

Mohs hardness
2-3
Color
Green
Luster
Vitreous
Streak
White
Density
2.25
Cleavage
Perfect on {010}
Fracture
Uneven
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Ilesite can be identified by its occurrence as ephemeral, secondary coatings and efflorescences in the oxidation zones of ore deposits, especially those rich in manganese, such as manganiferous sphalerite or alabandite. A key diagnostic feature is its complete solubility in water. Its pale green or pinkish color, low hardness, and vitreous luster are also helpful in identification. ## Distinguishing from Similar Minerals Ilesite is part of an isomorphic series with jokokuite (MnSO₄·4H₂O), szomolnokite (FeSO₄·H₂O), and rozenite (FeSO₄·4H₂O). Distinguishing it from rozenite, which has an identical structure and similar appearance, is macroscopically impossible and requires chemical analysis to determine the dominant cation (manganese or iron). Melanterite (FeSO₄·7H₂O), which contains more crystallization water and crystallizes in a different system, may have a similar appearance. ## Crystal Forms Ilesite crystals are extremely rare. If they occur, they take the form of short, prismatic columns. Most often, however, it forms aggregates in the form of crusts, coatings, efflorescences, and earthy or fibrous masses.

Geological environment

## Genesis Ilesite is a secondary mineral, formed by the oxidation (weathering) of sulfide ore deposits, especially those rich in manganese, such as manganiferous sphalerite or alabandite. It forms as a product of the evaporation of mine waters in dry conditions, often on the walls of old mine workings. It is an unstable mineral, forming and disappearing depending on seasonal changes in humidity. ## Mineral Associations This mineral co-occurs with other secondary sulfates, such as melanterite, rozenite, szomolnokite, gypsum, epsomite, as well as with the sulfides from which it originates, e.g., pyrite, sphalerite, galena, and alabandite. ## Localities The most important localities worldwide, from which well-documented specimens originate, include the Hall Valley Mine in Park County, Colorado, USA (type locality); the Veta-Grande Mine in Zacatecas, Mexico; the Consort Mine in Barberton, South Africa; as well as some mines in Germany (e.g., in the Harz Mountains) and Japan.

Rarity

Very rare

For collectors

## Quality Criteria The collector appeal of ilesite is low due to its instability and inconspicuous appearance. The most valued are rare, well-formed microcrystals. In the case of coatings and crusts, the intensity of color (greenish or pinkish) and the abundance of occurrence on the host rock fragment determine its value. Due to storage difficulties, it is a mineral sought mainly by specialized collectors of secondary and rare minerals. ## Popular Localities Specimens from the type locality - Hall Valley in Colorado - are of historical significance. Good quality material also came from the mine in Zacatecas, Mexico.

Care and storage

## Cleaning Ilesite is extremely sensitive to water and moisture. **Absolutely do not clean it with water or any liquids.** The only permissible method is to very gently remove dust with a soft, dry brush or a stream of compressed air from a distance. ## What to Avoid Avoid: - Water and all liquids - the mineral will dissolve in them. - Humid air - causes disintegration and deliquescence of the specimen. - High temperatures - can lead to dehydration and destruction of the structure. - Sudden temperature changes. - All chemicals, acids, and bases. ## Storage Ilesite specimens require specialized storage conditions. They should be kept in tightly sealed containers (e.g., "perky boxes") along with a moisture-absorbing agent, such as silica gel. Display should only take place in a controlled, dry environment. It is a very difficult mineral to preserve in collections.

External references

Sources

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