Parabutlerite

Chemical formula: Fe³⁺S⁶⁺O₄(OH)(H₂O)₂

Parabutlerite is a rare, secondary iron sulfate, forming aggregates of small, orange crystals with a vitreous or silky luster.

## Characteristics Parabutlerite is a hydrated iron sulfate, occurring in the oxidation zones of ore deposits. It forms aggregates of small, acicular or capillary crystals, which can create radial aggregates, crusts, or coatings. Individual crystals are usually small, rarely exceeding a few millimeters in length, but their aggregates can be visually striking. ## Physical Properties This mineral is characterized by a relatively low hardness, approximately 2.5 on the Mohs scale, meaning it can be scratched with a fingernail. It has a vitreous luster, and in the case of fine-fibrous aggregates, a silky luster. It is transparent to translucent. Its density is approximately 2.53 g/cm³. ## Colors and Varieties Parabutlerite occurs in characteristic shades of orange, from yellowish-orange to reddish-orange. No color or commercial varieties are distinguished. ## History and Name The mineral's name refers to its relationship with butlerite, with which it is dimorphous (having the same chemical composition but a different crystal structure). The prefix "para-" indicates this relationship. It was first described in 1938 based on material from the Alcaparrosa mine in the El Loa Province, Chile. ## Uses Parabutlerite has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals or secondary minerals from oxidation zones.

Properties

Mohs hardness
2.5
Color
Pale orange to pale orange-brown; light yellow in transmitted light.
Luster
Vitreous
Streak
Pale yellow
Density
2.55
Cleavage
On {110}, poor.
Fracture
Conchoidal
Transparency
Transparent to Translucent
Crystal system
Orthorhombic

Diagnostic features

## Identification Parabutlerite can be identified by its characteristic orange color, acicular or capillary crystal habit, and occurrence in paragenesis with other secondary sulfates. Its low hardness and reaction to water are also important clues. ## Distinguishing from Similar Minerals It can be confused with butlerite, which has an identical chemical composition but crystallizes in the monoclinic system. Distinguishing these two minerals without advanced studies (e.g., X-ray diffraction) is practically impossible. Other visually similar iron sulfates, such as copiapite, may have different shades (more often yellow) and aggregate forms. ## Crystal Forms Crystals are usually elongated, prismatic, acicular, or capillary. They often form radial or tangled aggregates, as well as crusty coatings on host rocks.

Geological environment

## Genesis Parabutlerite is a secondary mineral, formed by the oxidation of iron sulfides (mainly pyrite and marcasite) in a dry, desert climate. It forms as a weathering product in the oxidation zones of ore deposits, and also as a product of volcanic exhalations (fumaroles). ## Mineral Associations It often co-occurs with other sulfates, such as butlerite, copiapite, jarosite, melanterite, voltaite, as well as gypsum and pyrite. ## Localities The most important occurrences of this rare mineral are in Chile (Alcaparrosa mine, Chuquicamata), the United States (Jerome in Arizona; Iron Point in Nevada), Hungary (Recsk), and Italy (La Solfatara fumarolic fields near Naples).

Rarity

Rare

For collectors

## Quality Criteria The most valued by collectors are specimens with well-formed, distinct crystals of intense, orange color. Rich crusts covering a significant area of the host rock and aesthetic associations with other colorful secondary minerals enhance their attractiveness. Due to the small size of the crystals, specimens suitable for viewing under magnification (so-called microminerals) are most commonly found in collections. ## Popular Localities Specimens from the type locality in Chile (Alcaparrosa) and from the mine in Jerome, Arizona (USA) are considered classic and most desired by collectors.

Care and storage

## Cleaning Parabutlerite specimens are very delicate and sensitive to water. Cleaning should be kept to an absolute minimum. A soft brush can be used to dry-dust. Any contact with water, which can dissolve or damage the crystals, should be avoided. ## What to Avoid Water, cleaning solutions, ultrasonics, and all chemicals must be strictly avoided. The mineral is sensitive to humidity changes – overly dry air can cause dehydration and disintegration, while overly humid air can lead to its dissolution. It should be protected from direct sunlight and high temperatures. ## Storage It is recommended to store specimens in tightly sealed containers (e.g., "perky boxes") to maintain stable ambient humidity. Due to its fragility, it should be avoided to place it in areas exposed to vibrations or impacts.

External references

Sources

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