Mendigite

Chemical formula: Mn<sup>2+</sup><sub>5</sub>CaSi<sub>6</sub>O<sub>18</sub>

Mendigite is a very rare, colorless silicate mineral, occurring as small, lath-like crystals within volcanic lavas.

## Characteristics Mendigite is an extremely rare calcium and manganese silicate. It forms colorless, transparent crystals with a lath-like or tabular habit, reaching sizes up to 0.2 mm. It typically occurs as single, dispersed crystals within gas vesicles in phonolitic lavas. ## Physical Properties Mendigite crystals are characterized by a vitreous luster. Due to the extreme rarity and small size of the crystals, most physical properties, such as hardness or density, have not been precisely determined. ## History and Name The mineral's name comes from its discovery locality – the town of Mendig in the Eifel Mountains in Germany. It was first described in 1999 by G. Hentschel, C. L. Lenz, W. Schmahl, and H. Kroll.

Properties

Luster
Vitreous
Streak
White
Cleavage
Perfect on {100}
Fracture
Uneven
Transparency
Transparent
Crystal system
Triclinic

Diagnostic features

## Identification Identification of mendigite is almost exclusively possible using advanced analytical methods, such as X-ray diffraction (XRD) and chemical microanalysis (EDS/WDS), due to its small size and lack of characteristic visual features. It occurs in a specific geological environment. ## Distinguishing from similar minerals It can be confused with other colorless microminerals found in gas vesicles of volcanic rocks, such as sanidine or tridymite. Definitive differentiation requires specialized laboratory equipment. ## Crystal forms It forms elongated, lath-like or tabular crystals, often grouped into small, radial aggregates.

Geological environment

## Genesis Mendigite forms under high-temperature conditions in the late stages of magma crystallization. It crystallizes in vesicles and fractures within phonolitic lavas, being a product of volcanic activity. ## Mineral associations It co-occurs with other minerals typical of this environment, such as sanidine, aegirine, nepheline, leucite, apophyllite, natrolite, and magnetite. ## Localities The only confirmed locality for mendigite in the world is its type locality: the In den Dellen quarry near the town of Mendig, in the Eifel volcanic complex in Germany.

Rarity

Extremely rare

For collectors

## Quality criteria As a "micromount" status mineral, the only criterion for evaluation is the presence of well-formed, identifiable crystals on the rock matrix. Every analytically confirmed specimen is extremely valuable from a scientific and collector's point of view, regardless of aesthetics. ## Popular localities The entire known global supply comes from a single location – the In den Dellen quarry in Germany, making it one of the most sought-after microminerals among specialized collectors.

Care and storage

## Cleaning Due to its extreme rarity and delicacy, specimens containing mendigite (usually micromounts) should not be cleaned mechanically or chemically. Gentle dust removal with a photographic air blower is sufficient. ## What to avoid Avoid contact with any chemicals, ultrasonics, and sudden temperature changes. The crystals are brittle and susceptible to mechanical damage. ## Storage Specimens should be stored exclusively in specialized micromount boxes, protecting them from dust, shocks, and humidity. They should not be exposed to direct sunlight.

Sources

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