Slottaite

Chemical formula: SrFe<sup>3+</sup><sub>3</sub>(PO<sub>4</sub>)(S<sup>6+</sup>O<sub>4</sub>)(OH)<sub>6</sub>

Slottaite is an extremely rare strontium and iron sulfophosphate, forming microscopic, yellowish-brown tabular crystals.

## Characteristics Slottaite is a very rare mineral from the phosphate group, chemically classified as a strontium and iron sulfophosphate. It occurs as extremely small, tabular or platy crystals, rarely exceeding 0.2 mm in length. These crystals often form rosette-like or radial aggregates. Due to its microscopic size, it is a mineral primarily accessible to specialized collectors (so-called micromounters). ## Physical Properties Slottaite crystals exhibit a vitreous luster. Hardness and density have not been precisely measured due to the small size of the samples, but the hardness is estimated to be around 4 on the Mohs scale. It is a brittle mineral. ## Colors and Varieties Slottaite has a characteristic, uniform yellow to yellowish-brown color. No color varieties or commercial forms are known. ## History and Name The mineral was approved by the International Mineralogical Association (IMA) in 2017 under the number IMA2017-041. Its name honors Terry Slotta (born 1948), an American mineral collector from California, who specializes in microminerals and is known for his contributions to their study. The type locality from which it originates is the Schooner Mine in Lander County, Nevada, USA. ## Applications Slottaite has no industrial applications. Its significance is purely scientific and collectible, being an object of desire among collectors of microscopic minerals.

Properties

Mohs hardness
4
Luster
Vitreous
Streak
Light yellow
Cleavage
Perfect on {0001}
Fracture
Brittle
Transparency
Translucent
Crystal system
Trigonal

Diagnostic features

## Identification Amateur identification of slottaite is practically impossible due to the microscopic size of the crystals. Recognition requires advanced analytical techniques, such as Raman spectroscopy or chemical analysis using an electron microprobe (EDS/WDS). Visually, it can be suspected based on its yellowish-brown color, tabular habit, and occurrence in association with other rare phosphates from Nevada. ## Distinguishing from Similar Minerals It can be confused with other microscopic, yellow or brown secondary minerals, such as jarosite, beudantite, or segnitite, which may occur in similar environments. Definitive differentiation is possible only through chemical analysis, which will reveal the unique combination of strontium, iron, phosphorus, and sulfur. ## Crystal Forms Slottaite forms very small, thin, tabular crystals with a hexagonal outline, flattened parallel to the {001} plane. These crystals often combine into small, rosette-like or radial aggregates.

Geological environment

## Genesis Slottaite is a secondary mineral that forms in the oxidation zones (gossans) of hydrothermal polymetallic deposits. It forms as a result of the weathering of earlier ore and phosphate minerals in a sulfate-rich environment. ## Mineral Associations At the type locality (Schooner Mine, Nevada, USA), slottaite co-occurs with minerals such as quartz, goethite, jarosite, segnitite, beudantite, corkite, hinsdalite, pyromorphite, wavellite, and minerals from the alunogen-meta-alunogen group. ## Localities The only confirmed and described occurrence of slottaite in the world is its type locality: the Schooner Mine (part of the Gold-Quartz mine complex), in the Bullion District, Lander County, Nevada, USA.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a slottaite specimen is primarily assessed based on the abundance and development of its microscopic crystals. Samples with numerous, sharp, well-formed crystals creating aesthetic aggregates are most highly valued. Association with other rare minerals also increases the scientific and collectible value of the specimen. Contrast with the host rock (matrix) also affects visual appeal. ## Popular Localities The only source of specimens is the Schooner Mine in Nevada, USA. All samples available on the collector's market originate from this single location.

Care and storage

## Cleaning Slottaite specimens are extremely small and fragile. Any mechanical cleaning should be avoided. If absolutely necessary, compressed air can be used from a safe distance to remove loose dust particles. Contact with water or other chemicals is not recommended. ## What to Avoid Avoid contact with all chemicals, especially acids. The crystals are very delicate, so vibrations, shocks, and touching should be avoided. Samples should be protected from dust and moisture. ## Storage It is recommended to store specimens exclusively in specialized, sealed micromount boxes, which protect them from mechanical damage and contamination. The box should be properly labeled.

Sources

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