Vladimirite

Chemical formula: Ca₄(As⁵⁺O₄)₂(As⁵⁺O₃OH)·₄H₂O

Vladimirite is a rare, hydrated calcium arsenate, forming colorless or pale pink, tabular crystals and radial aggregates.

## Characteristics Vladimirite is a rare mineral from the arsenate group, chemically classified as a hydrated calcium arsenate. It occurs as small, tabular or bladed crystals, which often form fan-shaped, radial, or spherulitic aggregates. Specimens are usually small, and well-formed crystals are rare. ## Physical Properties This mineral is characterized by a hardness of 3.5 on the Mohs scale, making it relatively soft. It has a density of approximately 3.12 g/cm³. Crystals exhibit a vitreous luster, and a pearly luster on cleavage surfaces. They are transparent to translucent. ## Colors and Varieties Vladimirite is most commonly colorless or white. Specimens with a delicate, pale pink coloration are also found. No named varieties are distinguished. ## History and Name The mineral was first described in 1953. Its name comes from one of its type localities – the Vladimirovskoye cobalt deposit in the Altai Republic, Russia. The second type locality is the Khovu-Aksy nickel-cobalt deposit in Tuva, also in Russia. ## Uses Due to its rarity and small crystal size, vladimirite has no industrial application. It is solely an object of interest for collectors of rare minerals.

Properties

Mohs hardness: 3.5
Luster: Vitreous, Pearly
Streak: White
Density: 3.12
Cleavage: Perfect on {010}
Fracture: Uneven
Transparency: Transparent,Translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Characteristic features of vladimirite are its forms of occurrence – small, tabular crystals gathered in radial or fan-shaped aggregates. Luster, relatively low hardness, and co-occurrence with other arsenates in the oxidation zones of ore deposits are key indicators. ## Distinguishing from Similar Minerals Vladimirite can be confused with other secondary arsenates or sulfates, such as gypsum or pharmacolite. It differs from gypsum by its higher density and different environment of occurrence. Distinguishing it from pharmacolite, which is also a calcium arsenate, can be difficult and often requires chemical or crystallographic analysis, although pharmacolite more often forms acicular or fibrous aggregates. ## Crystal Forms Crystals are tabular, flattened parallel to {010} and elongated along the a-axis. They most often form fan-shaped, radial, spherulitic, or rosette-like aggregates and crusts.

Geological environment

## Genesis Vladimirite is a secondary mineral, formed in the oxidation (weathering) zones of arsenic-rich ore deposits, especially in the presence of calcium-rich rocks (e.g., limestones, dolomites). It forms as a result of the reaction of solutions containing arsenic acid with calcium minerals. ## Mineral Associations This mineral often co-occurs with other arsenates, such as erythrite, annabergite, pharmacolite, picropharmakolite, sainfeldite, rauenthalite, as well as with calcite and gypsum. ## Localities The most important and classic localities for vladimirite are in Russia – at the discovery site in the Khovu-Aksy deposit (Tuva) and in the Vladimirovskoye deposit (Altai). Outside Russia, its occurrence has been noted, among others, in the Bou Azzer mines in Morocco, in Sterling Hill in New Jersey (USA), and in Saxony in Germany.

Rarity

Rare

For collectors

## Quality Criteria The most valued by collectors are specimens with well-formed, sharp crystals forming aesthetic, fan-shaped or radial aggregates. Specimens where colorless or pink vladimirite crystals contrast with dark matrix rock are desirable. The size of the aggregates and the clarity of the crystals also significantly increase the value of the specimen. ## Popular Localities The best specimens in the world are considered to come from historical localities in Russia and from the Bou Azzer region in Morocco, from where many well-formed specimens of this mineral originate.

Care and storage

## Cleaning Vladimirite specimens should be cleaned very carefully, using a soft brush to remove dust. Brief rinsing in distilled water is permissible, followed by thorough drying. Ultrasonic cleaners should be avoided. ## What to Avoid As an arsenate, the mineral is toxic – avoid inhaling dust and wash hands after any contact. It is sensitive to acids and high temperatures, which can lead to dehydration and destruction of its structure. It should be protected from prolonged exposure to moisture. ## Storage It is recommended to store specimens in a dry place, in closed boxes or display cases, to protect them from dust and mechanical damage. Keep it away from children and pets due to its arsenic content.