Olsacherite

Chemical formula: Pb²⁺₂(Se⁶⁺O₄)(S⁶⁺O₄)

Olsacherite is a very rare lead selenite-sulfate, forming tiny, colorless to white acicular or bladed crystals.

## Characteristics Olsacherite is a mineral from the selenite and sulfate group, chemically classified as a lead selenite-sulfate. It occurs as very small, elongated crystals with an acicular or bladed habit, which can form radial aggregates or tangled masses. Individual crystals are typically colorless to white and transparent, which, combined with their small size, makes them difficult to observe with the naked eye. ## Physical Properties Olsacherite crystals exhibit a luster described as vitreous to adamantine. Due to their small size and rarity, many of its physical properties, such as hardness or density, have not been precisely determined. ## History and Name The mineral was named in honor of Juan Augusto Olsacher (1893-1964), an Argentinian mineralogist and curator of the mineralogical collection at the National University of Córdoba in Argentina. It was described and approved as a new mineral species in 1969. ## Uses Olsacherite has no industrial applications. Its significance is purely scientific and collectible, being a coveted item for specialized collectors of rare minerals.

Properties

Mohs hardness
3-3.5
Color
Colorless
Luster
Vitreous to adamantine
Streak
white
Density
0
Cleavage
{101} good, {010} fair
Fracture
Uneven
Transparency
Transparent,Translucent
Crystal system
Orthorhombic

Diagnostic features

## Identification Identification of olsacherite requires advanced analytical methods, such as Raman spectroscopy or X-ray diffraction (XRD), due to its small size and similarity to other secondary lead minerals. Visually, it is characterized by occurring as tiny, colorless, acicular crystals in association with other selenites. ## Distinguishing from similar minerals It can be confused with other lead sulfates or selenites, such as anglesite, linarite, or schmiederite, with which it often co-occurs. Definitive differentiation is almost exclusively possible based on chemical analysis confirming the simultaneous presence of selenite and sulfate groups. ## Crystal forms It forms elongated, acicular or bladed crystals, often grouped into radial or chaotic aggregates. Crystals are usually very small, reaching lengths of up to about 1 mm.

Geological environment

## Genesis Olsacherite is a secondary mineral formed in the oxidation (weathering) zones of ore deposits containing selenium minerals and lead sulfides. It forms under low temperature and pressure conditions as a result of oxygen-rich waters acting on primary ores. ## Mineral associations It co-occurs with other secondary lead minerals, such as anglesite, cerussite, linarite, schmiederite, as well as with molybdenite, pyrite, and quartz. ## Localities The most important and type locality for this mineral is the Hiaco mine (Pacajake) in the Colquechaca Province, Bolivia. This is the only confirmed locality from which well-characterized olsacherite specimens originate.

Rarity

Very rare

For collectors

## Quality criteria The most highly valued specimens are those showing well-formed, even if microscopic, acicular olsacherite crystals, forming rich aggregates on the rock matrix. Contrast with other minerals, such as blue linarite, significantly enhances the visual appeal and value of the specimen. Due to its rarity, every confirmed specimen holds great value for specialized collectors. ## Popular localities The only source of collectible specimens is the Hiaco mine in Bolivia. Specimens from this locality are considered classic and most desirable.

Care and storage

## Cleaning Specimens should be cleaned only very carefully, using compressed air to remove dust. Contact with water or other chemicals is absolutely inadvisable due to the mineral's potential solubility and fragility. ## What to avoid Avoid all chemical agents, ultrasonics, and sudden temperature changes. The mineral is very delicate and sensitive to mechanical shocks. It should not be exposed to direct sunlight. ## Storage It is recommended to store specimens under stable conditions, in enclosed, padded "micromount" boxes, to protect them from dust, mechanical damage, and humidity changes.

External references

Sources

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