Voglite

Chemical formula: Ca<sub>2</sub>Cu<sup>2+</sup>(U<sup>6+</sup>O<sub>2</sub>)(CO<sub>3</sub>)<sub>4</sub>·6H<sub>2</sub>O

Voglite is a rare, secondary uranyl mineral, forming aggregates of tiny, scaly crystals with an intensely emerald-green color.

## Characteristics Voglite is a hydrated calcium, copper, and uranyl carbonate. It occurs in the oxidation zones of uranium deposits. It forms very small, scaly or bladed crystals, which typically form rosette aggregates, crusts, or earthy masses. Due to the small size of the crystals, its macroscopic features are difficult to observe without magnification. ## Physical Properties Voglite crystals are soft and brittle, with a Mohs hardness of 2-2.5. They have a vitreous luster, and a pearly luster on cleavage surfaces. They are transparent to translucent. The mineral's density is approximately 3.35 g/cm³. ## Colors and Varieties Voglite is characterized by a vivid, emerald-green to grass-green color. No color varieties or commercial varieties are distinguished. ## History and Name The mineral was named in honor of Josef Florian Vogl (1818-1896), an Austrian mining official and mineralogist, who first described this mineral in 1853. The type locality (where it was discovered) is Jáchymov (St. Joachimsthal) in the Czech Republic. ## Uses Voglite, due to its rarity and small crystal size, has no industrial applications. It is of scientific and collector's interest only.

Properties

Mohs hardness
2-2.5
Luster
Vitreous, Pearly
Streak
Light green
Density
3.35
Cleavage
Perfect on {010}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Monoclinic

Diagnostic features

## Identification A characteristic feature of voglite is its intensely emerald-green color and its occurrence in the form of tiny, scaly crystals forming rosette aggregates or crusts. Co-occurrence with other secondary uranium minerals is also an important indicator. ## Distinguishing from Similar Minerals Voglite can be confused with other green, secondary uranium minerals, such as cuprosklodowskite, torbernite, or zeunerite. Differentiation often requires chemical analysis (EDS) or X-ray diffraction (XRD), as they can be very similar macroscopically. However, voglite is distinguished by its characteristic scaly habit, while torbernite and zeunerite usually form tabular crystals with a square outline. ## Crystal Forms Crystals are very small, scaly or bladed in habit, often elongated. They typically form spherical or rosette aggregates, as well as thin crusts and coatings on the host rock.

Geological environment

## Genesis Voglite is a secondary mineral, formed in the oxidation zones of hydrothermal uranium-bearing deposits. It forms as a result of the weathering of primary uranium minerals, such as uraninite, in the presence of copper- and carbonate-rich solutions. ## Mineral Associations It most commonly co-occurs with other secondary uranium minerals, such as liebigite, schröckingerite, cuprosklodowskite, uraninite, as well as with gypsum, fluorite, and quartz. ## Localities The most important occurrences of voglite are the historic mines in Jáchymov (Czech Republic), from where the type material originates. It is also known from several localities in the USA, especially from Utah (Delta, Lucky Strike mines), and also from Germany (Saxony).

Rarity

Rare

For collectors

## Quality Criteria For collectors, the most desirable specimens are those with well-formed, distinct rosette aggregates of an intense, emerald-green color. Rich crusts covering a significant area of the rock matrix are also highly valued. Contrast with a light host rock enhances the visual appeal of the specimen. ## Popular Localities The most classic and prized specimens come from the type locality in Jáchymov, Czech Republic. Specimens from mines in Utah (USA) also provide good quality collector's material, often in the form of rich crusts.

Care and storage

## Cleaning Voglite specimens are extremely delicate and brittle. They should only be cleaned very carefully, using compressed air to remove dust. Any contact with water or chemicals is inadvisable and can lead to damage or dissolution of the mineral. ## What to Avoid Avoid contact with water and all liquids. The mineral is sensitive to changes in temperature and humidity. As a uranium mineral, voglite is radioactive and should be handled with appropriate precautions – avoid inhaling dust and wash hands after each contact. ## Storage Voglite specimens should be stored in sealed, stable containers (e.g., "micromount" type) to protect them from mechanical damage, dust, and humidity changes. They should be stored away from other minerals that could be damaged by its radiation.

Sources

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