Scordariite

Chemical formula: K<sub>8</sub>(Fe<sup>3+</sup><sub>0.67</sub>&#9744;<sub>0.33</sub>)[Fe<sup>3+</sup><sub>3</sub>O(S<sup>6+</sup>O<sub>4</sub>)<sub>6</sub>(H<sub>2</sub>O)<sub>3</sub>]<sub>2</sub>(H<sub>2</sub>O)<sub>11</sub>

Scordariite is a very rare iron and potassium sulfate, forming microscopic, platy, yellow crystals.

## Characteristics Scordariite is a hydrated iron and potassium sulfate belonging to the jarosite group. It occurs as very fine, platy crystals with a hexagonal outline, rarely exceeding 20 micrometers in size. These crystals form aggregates and coatings. Due to the microscopic size of the crystals, visual features are difficult to observe without specialized equipment. ## Physical Properties Scordariite crystals exhibit yellow pleochroism. The luster is vitreous. Due to the microscopic size of the crystals, hardness and density have not been precisely measured, but only calculated based on the chemical formula and unit cell parameters. ## Colors and Varieties This mineral has a characteristic yellow color. No varieties have been distinguished. ## History and Name The mineral's name honors Professor Francesco Scordari (born in 1943) from the University of Bari, Italy, in recognition of his contributions to the crystal chemistry of sulfates. Scordariite was first described in 2011 after being found in the mine dumps of La Alcaparrosa in Spain. It was approved by the International Mineralogical Association (IMA) under number 2010-060.

Properties

Luster
Vitreous
Streak
Yellow
Density
2.81
Cleavage
Perfect on {0001}
Transparency
Transparent
Crystal system
Trigonal

Diagnostic features

## Identification Identification of scordariite is possible only through advanced laboratory methods, such as X-ray diffraction (XRD) and chemical microanalysis (EDS/WDS). It is impossible to perform under collector or field conditions. ## Distinguishing from Similar Minerals Scordariite is visually indistinguishable from other minerals of the jarosite group, such as jarosite itself, natrojarosite, or hydroniumjarosite. Differences can only be determined based on detailed chemical and structural analysis. ## Crystal Forms It forms microscopic, platy crystals with a hexagonal outline, usually gathered in small aggregates.

Geological environment

## Genesis Scordariite is a secondary mineral, forming in the oxidation zones (gossans) of sulfide deposits in dry or semi-arid climates. It forms as a result of the weathering of iron- and sulfide-containing minerals in a potassium-rich environment. ## Mineral Associations It most commonly co-occurs with other minerals from the jarosite group, as well as with quartz, gypsum, and hematite. ## Localities The only confirmed occurrence (type locality) is the La Alcaparrosa mine, in the province of Almería, Andalusia (Spain).

Rarity

Extremely rare

For collectors

## Quality Criteria As a microscopic mineral, scordariite is not evaluated based on typical aesthetic criteria such as color or luster visible to the naked eye. The scientific and collector value of a specimen depends on the confirmation of its identity, the abundance of its occurrence on the matrix, and the quality of the analysis that identified it. Specimens are significant only for specialized micromount collections and scientific institutions.

Care and storage

## Cleaning Due to its extreme rarity and microscopic nature, scordariite specimens should not be cleaned under amateur conditions. Any procedures require specialized laboratory equipment. ## What to Avoid Avoid contact with water, chemicals, as well as any shocks and abrasion that could destroy the delicate, microscopic crystals. ## Storage Specimens should be stored under stable conditions, in specialized, sealed containers (so-called micromount boxes), protecting them from dust, moisture, and mechanical damage.

Sources

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