Vendidaite

Chemical formula: Al₂(S₆+O₄)(OH)₃ Cl·₆H₂O

Vendidait is a very rare, hydrated aluminum sulfate with chlorine, forming small, colorless or white bladed crystals.

## Characteristics Vendidait is a mineral from the sulfate group, chemically classified as a hydrated basic aluminum sulfate with chlorine. It occurs as very small, elongated crystals with a bladed habit, typically not exceeding 0.2 mm in length. These crystals are colorless to white and form small, radial aggregates or coatings on the surface of the host rock. Due to the small size of the crystals, its visual features are difficult to observe without magnification. ## Physical Properties Vendidait crystals exhibit a vitreous luster. This mineral is transparent. Its hardness on the Mohs scale is very low, at 1.5, which means it is extremely soft and easily scratched. The density calculated based on the chemical formula and unit cell parameters is 1.95 g/cm³. ## History and Name Vendidait was first described in 2016 by Anthony R. Kampf and his team. The mineral's name comes from its discovery locality – the Wendy mine, located in the Vendida polymetallic deposit in the Sierra Gorda district, Antofagasta Province, Chile. The name is a combination of the deposit name ("Vendida") and the mine name ("Wendy"). The mineral was approved by the International Mineralogical Association (IMA) under number IMA2016-042. ## Uses Vendidait has no industrial applications. Its significance is purely scientific and as a collector's item, being a very rare and recently discovered mineral species.

Properties

Mohs hardness: 1.5
Luster: Vitreous
Streak: White
Density: 1.95
Cleavage: Perfect on {100}
Fracture: Uneven
Transparency: Transparent
Crystal system: Monoclinic

Diagnostic features

## Identification Amateur identification of vendidait is practically impossible. This mineral forms microscopic, colorless crystals that require specialized equipment for analysis. Definitive identification relies on advanced techniques such as X-ray diffraction (XRD) and chemical analysis (EDS), which allow its composition and crystal structure to be determined. ## Distinguishing from Similar Minerals Vendidait can be confused with many other secondary sulfates, such as gypsum, chalcanthite (in the form of colorless crystals), or other rare aluminum sulfate minerals. Distinguishing it from these minerals based on visual characteristics is impossible. Key factors are its co-occurrence with other rare minerals in the specific geological environment of the Wendy mine and confirmation of its chemical composition (presence of aluminum, sulfur, and chlorine). ## Crystal Forms Vendidait crystallizes as elongated, bladed crystals, flattened along one of the crystallographic axes. These crystals often form small, radial or chaotically arranged aggregates on the rock surface.

Geological environment

## Genesis Vendidait is a secondary mineral formed as a result of weathering (oxidation) processes of primary sulfide deposits in a very arid (desert) climate. Its formation is associated with the interaction of sulfate- and chloride-rich solutions with aluminum-containing minerals. It is a typical mineral of the oxidation zone (gossan) of polymetallic deposits. ## Mineral Associations This mineral occurs in association with other rare sulfates and halides. At its type locality (Wendy mine), it was found in association with aubertite, chalcanthite, eriostoranite, jurbanite, magnesiocopiapite, metavoltine, romerite, and tamarugite. ## Localities The only confirmed occurrence of vendidait in the world is its type locality: the Wendy mine in the Vendida deposit, in the Sierra Gorda district, Antofagasta Province, in the Atacama Desert, Chile.

Rarity

Extremely rare

For collectors

## Quality Criteria As a "micromount" mineral, the collector's value of vendidait primarily depends on the quality and richness of the crystal aggregates on the rock matrix. The most desirable specimens are those with clearly formed, radial crystal clusters that are well visible under a microscope. Contrast with the substrate and the presence of interesting associated minerals are also important. ## Popular Localities The only source of vendidait specimens is the Wendy mine in Chile. Material from this locality is extremely rare and sought after by specialized "micromount" mineral collectors.

Care and storage

## Cleaning Vendidait specimens should be handled with extreme caution due to their extreme fragility and small crystal size. Mechanical cleaning is highly inadvisable. If absolutely necessary, compressed air can be used from a safe distance to remove loose dust particles. ## What to Avoid The mineral is likely water-soluble, so all contact with liquids should be avoided. It should be protected from chemicals, high temperatures, and humidity. Due to its very low hardness (1.5 on the Mohs scale), it is extremely susceptible to mechanical damage – even touch can destroy the delicate crystals. ## Storage Vendidait specimens should be stored exclusively in specialized, sealed "micromount" boxes that protect them from dust, humidity, and physical damage. It should not be stored with other minerals that could scratch or damage it.

Sources

IMA Mineral List (CNMNC)