Voudourisite

Chemical formula: Cd₂+S₆+O₄·H₂O

Voudourisite is an extremely rare, hydrated cadmium sulfate, forming colorless, acicular crystals in the oxidation zones of sulfide deposits.

## Characteristics Voudourisite is a hydrated cadmium sulfate, belonging to secondary minerals. It occurs as colorless, transparent acicular crystals, elongated in one direction. These crystals reach up to 1 mm in length and most often form radial or divergent aggregates, resembling small hedgehogs or fans. Due to its chemical composition and rarity, it is primarily of scientific interest. ## Physical Properties The mineral is characterized by a vitreous luster and is completely transparent. Its hardness and density have not yet been precisely measured due to the small size and rarity of the crystals. It is brittle and delicate. ## Colors and Varieties Voudourisite is colorless. No colored varieties or trade names are known. ## History and Name The mineral was officially recognized by the International Mineralogical Association (IMA) in 2011. Its name honors Panagiotis Voudouris, professor of mineralogy and ore geology at the University of Athens, in recognition of his contributions to mineralogical research of the historic mining district of Laurion in Greece. ## Applications Due to its extreme rarity and microscopic crystal size, voudourisite has no industrial applications. It is exclusively a valuable object for scientific research and advanced specialized collections (so-called microminerals).

Properties

Luster: Vitreous
Streak: White
Cleavage: None
Transparency: Transparent
Crystal system: Monoclinic

Diagnostic features

## Identification Amateur identification of voudourisite is practically impossible. Key indicators include its specific location (Hilarion mine in Laurion), acicular crystal habit forming radial aggregates, and co-occurrence with other secondary sulfide minerals. Definitive identification requires advanced analytical methods, such as X-ray diffraction (XRD) and chemical microanalysis (EDS). ## Distinguishing from Similar Minerals It can be confused with other colorless, acicular secondary minerals found in Laurion, such as gypsum or other rare sulfates. Gypsum is significantly softer. Final differentiation from similar rare minerals is possible only through laboratory analysis. ## Crystal Forms It exclusively forms acicular crystals, which combine into characteristic, small aggregates with a radial or fan-like structure.

Geological environment

## Genesis Voudourisite is a secondary mineral, forming in the oxidation (supergene) zone of polymetallic sulfide deposits. It crystallizes as a result of the weathering of primary cadmium-bearing minerals, such as greenockite or cadmium-rich sphalerite, in the presence of sulfate solutions. ## Mineral Associations It most often co-occurs with gypsum, greenockite, niedermayrite, as well as with remnants of primary sulfides, such as sphalerite, pyrite, and galena. ## Localities The only confirmed locality of voudourisite in the world is its type locality – the Hilarion mine in Kamariza, in the historic mining district of Laurion (Lavrion) in Greece.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of voudourisite specimens, which are exclusively microminerals, is assessed based on several criteria. The most highly valued are rich clusters of well-formed, radial aggregates on a small rock matrix. The size and luster of individual needles, as well as the absence of damage, are important. Aesthetic co-occurrence with other minerals, e.g., color-contrasting greenockite, also enhances its attractiveness. ## Popular Localities The only source of collector specimens is the Hilarion mine in Laurion (Greece). This mineral is available exclusively on the specialized micromineral market and is sought after by collectors specializing in rare species or minerals from this specific locality.

Care and storage

## Cleaning Voudourisite crystals are extremely delicate and potentially water-soluble. Cleaning should be limited to an absolute minimum. Only careful dust removal with a soft, dry brush or a gentle stream of compressed air from a safe distance is permissible. ## What to Avoid Contact with water and any chemical agents that could damage or dissolve the mineral must be strictly avoided. Specimens are very sensitive to shocks and mechanical damage – acicular crystals are easily destroyed. High humidity should also be avoided. ## Storage It is recommended to store specimens in sealed, closed "micromount" boxes that protect against dust, moisture, and mechanical damage. Display should be away from sources of vibration.

Sources

IMA Mineral List (CNMNC)