Alterite

Chemical formula: Zn<sup>2+</sup><sub>2</sub>Fe<sup>3+</sup><sub>4</sub>(S<sup>6+</sup>O<sub>4</sub>)<sub>4</sub>((C<sub>2</sub>)<sup>6+</sup>O<sub>4</sub>)<sub>2</sub>(OH)<sub>4</sub>·17H<sub>2</sub>O

Alterite is an extremely rare hydrated zinc and iron sulfate and oxalate, forming acicular crystals in its only known locality worldwide.

## Characteristics Alterite is a complex secondary mineral, a hydrated zinc and iron sulfate and oxalate. It occurs as delicate, acicular crystals of a pale yellow color, forming radial aggregates and clusters. Individual crystals rarely exceed 1 mm in length, classifying alterite as a typical micromineral. Its unique chemical composition, combining sulfate and oxalate ions, is a result of specific processes occurring in the mine environment. ## Physical Properties This mineral is very soft, with a Mohs hardness of about 2, meaning it can be scratched with a fingernail. It exhibits a vitreous luster and is transparent. Its density, calculated based on the formula and unit cell parameters, is 2.43 g/cm³. It is brittle and requires careful handling. ## Colors and Varieties Alterite is known exclusively in one color – pale yellow. No color varieties or commercial forms have been described. ## History and Name The mineral's name honors the Alter family, who owned the White Caps Mine in Nevada (USA), where the discovery was made. It was officially recognized by the International Mineralogical Association (IMA) in 2016 under the number IMA2016-056. Its discovery and description exemplify relatively new mineralogy. ## Applications Due to its extreme rarity, small crystal size, and instability, alterite has no industrial applications. It is solely an object of scientific and collecting interest, being a valuable acquisition for specialized collections of rare minerals.

Properties

Mohs hardness
2
Luster
Vitreous
Streak
Light yellow
Density
2.43
Cleavage
None
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of alterite in the field or collection is based on its characteristic appearance – radial aggregates of small, acicular crystals of a pale yellow color. Its locality (White Caps Mine) and co-occurrence with other secondary sulfates are crucial. Since it is a micromineral, a microscope is essential for observation. ## Distinguishing from similar minerals Alterite can be visually confused with other secondary, yellow acicular minerals such as jarosite, copiapite, or metavoltine. Definitive differentiation is almost exclusively possible using advanced analytical methods, such as Raman spectroscopy or X-ray diffraction (XRD), which can confirm its unique chemical composition containing both sulfates and oxalates. ## Crystal forms It forms exclusively acicular crystals. These crystals most often occur as radial or chaotic aggregates and clusters on the host rock.

Geological environment

## Genesis Alterite is a secondary mineral of post-mining genesis. It forms in old mine workings as a result of complex chemical reactions. This process involves the oxidation of primary sulfide ores (source of zinc, iron, and sulfates) and the interaction of the resulting acidic mine waters with organic matter, such as wooden mine timbers, which are a source of oxalic acid. ## Mineral associations At its type locality, alterite co-occurs with other secondary minerals, mainly sulfates, such as gypsum, coquimbite, and voltaite. ## Localities The only confirmed locality of alterite in the world is its type locality – the White Caps Mine, Nye County, Nevada, USA.

Rarity

Extremely rare

For collectors

## Quality criteria The quality of an alterite specimen, being a micromineral, is assessed based on several factors. The most important is the abundance and density of crystal aggregates on the rock matrix. Specimens with clearly formed, radial "suns" of acicular crystals are more highly valued. The intensity and purity of the yellow color, as well as aesthetic arrangement on a small matrix, increase its collector's value. Contrast with the color of the host rock is also desirable. ## Popular localities The only source of alterite specimens is its type locality – the White Caps Mine in Nevada. All specimens available on the collector's market come from this single location, making them particularly sought after by collectors specializing in rare minerals and type locality specimens.

Care and storage

## Cleaning Alterite is an extremely delicate mineral and likely sensitive to water. Cleaning should be kept to an absolute minimum. Only very careful dust removal with a soft brush or a stream of compressed air from a distance is permissible. Any contact with water and chemical agents should be avoided. ## What to avoid Absolutely avoid water, ultrasonic cleaners, steam, and all solvents. The mineral is very soft, so it must be protected from impacts, scratches, and vibrations. High humidity and sudden temperature changes should also be avoided. ## Storage Alterite specimens should be stored in stable, dry conditions. The best solution is a sealed "perky box" type container, which protects against dust, mechanical damage, and humidity fluctuations. It should be kept away from direct sunlight.

External references

Sources

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