Magnesiofluckite

Chemical formula: CaMg(As<sup>5+</sup>O<sub>3</sub>OH)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>

Magnesiofluckite is an extremely rare calcium and magnesium arsenate, forming colorless, acicular crystals in radial aggregates.

## Characteristics Magnesiofluckite is a hydrated calcium and magnesium arsenate. It occurs as very small, colorless crystals with an elongated, bladed or acicular habit. These crystals typically form radial or spherulitic aggregates, less commonly appearing as single, isolated individuals. Due to the small size of the crystals, its visual features are difficult to observe without magnification. ## Physical Properties This mineral is characterized by a vitreous luster and is transparent. Its calculated density is approximately 3.16 g/cm³. Hardness has not been precisely determined. ## Colors and Varieties Magnesiofluckite is colorless. No colored varieties are known. ## History and Name The mineral's name refers to its chemical composition – the presence of magnesium (Magnesio-) and its structural similarity to fluckite (CaMn(AsO₃OH)₂(H₂O)₂), of which it is the magnesium analogue. It was first described in 1999 by a team of mineralogists led by P. Ondruš, based on material from the Svornost mine in Jáchymov, Czech Republic. ## Applications Due to its extreme rarity and microscopic crystal sizes, magnesiofluckite has no practical applications and is solely an object of scientific and collecting interest for specialized rare mineral collectors.

Properties

Luster
Vitreous
Streak
White
Density
3.16
Cleavage
Perfect on {010}, Good on {100} and {001}
Transparency
Transparent
Crystal system
Triclinic

Diagnostic features

## Identification Identification of magnesiofluckite is almost exclusively possible using advanced analytical methods, such as X-ray diffraction (XRD) and chemical microanalysis (EDS/WDS). Visually, it is characterized by colorless, acicular crystals forming radial aggregates. ## Distinguishing from Similar Minerals It can be confused with other rare, secondary arsenates of similar appearance, such as pharmacolite, picropharmacolite, or fluckite. Differentiation from pharmacolite (Ca(AsO₃OH)·2H₂O) and picropharmacolite (Ca₄Mg(AsO₄)₂(AsO₃OH)₂·11H₂O) requires chemical analysis. From fluckite, its manganese analogue, it differs by the dominance of magnesium over manganese in its composition. ## Crystal Forms It forms thin, bladed or acicular crystals, elongated along the [100] axis. Most often, they occur as radial, stellate, or spherulitic aggregates.

Geological environment

## Genesis It is a secondary mineral, forming in the oxidation zones of arsenical ores in hydrothermal deposits. It forms as a result of the weathering of primary arsenic-bearing minerals in an environment rich in calcium and magnesium. ## Mineral Associations It co-occurs with other secondary arsenates, such as picropharmacolite, pharmacolite, haidingerite, and native arsenic. ## Localities The only confirmed locality of magnesiofluckite in the world is its type locality – the Svornost mine in Jáchymov (formerly St. Joachimsthal) in the Czech Republic.

Rarity

Extremely rare

For collectors

## Quality Criteria For such a rare mineral, the main criterion is the confirmation of its presence on the sample itself. Specimens with well-formed, visible under magnification crystal aggregates, rich in magnesiofluckite and contrasting with the rock matrix, are most highly valued. Good documentation of origin and confirming analysis is also important. ## Popular Localities The only source of specimens is the Svornost mine in Jáchymov, Czech Republic.

Care and storage

## Cleaning Specimens should be cleaned only very carefully, using compressed air to remove dust. Any contact with water or chemicals is not recommended. ## What to Avoid Avoid contact with water, acids, and other chemicals that can damage the delicate crystals. The mineral is brittle and susceptible to mechanical damage. Protect it from high temperatures and sudden temperature changes. ## Storage Store in stable conditions, in a closed, padded "micromount" box to protect it from dust, moisture, and physical damage.

Sources

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