Manganlotharmeyerite

Chemical formula: CaMn<sup>3+</sup><sub>2</sub>(As<sup>5+</sup>O<sub>4</sub>)<sub>2</sub>(OH)<sub>2</sub>

A rare calcium and manganese arsenate, forming microscopic, reddish-brown crystals with a vitreous luster.

## Characteristics Manganlotharmeyerite is a mineral from the arsenate group, belonging to the tsumcorite group. It occurs as very small, tabular or bladed crystals, rarely exceeding 0.1 mm in length. These crystals often form radial aggregates or rosettes. Due to its size, it is a mineral primarily accessible to micromounters. ## Physical Properties Crystals exhibit a vitreous luster. The Mohs hardness is approximately 4.5. The mineral is brittle and has an uneven fracture. The calculated density is 4.49 g/cm³. ## Colors and Varieties This mineral has a characteristic reddish-brown to dark red color. The streak is light brown. No color or commercial varieties are distinguished. ## History and Name The name manganlotharmeyerite refers to its chemical composition – the dominance of manganese (Mn) – and its relation to lotharmeyerite, in which manganese replaces zinc. It was described as a new mineral in 1999 by P. Orlandi, S. V. Soboleva, M. G. Yuditskaya, and S. A. Vakhnina based on samples from the Krupka mine in the Czech Republic.

Properties

Mohs hardness
4.5
Luster
Vitreous
Streak
Light brown
Density
4.49
Cleavage
Good on {010}
Fracture
Uneven
Transparency
Translucent to opaque
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of manganlotharmeyerite is possible almost exclusively based on chemical analysis (EDS/WDS) and crystallographic analysis (XRD) due to its microscopic size and occurrence. In a collection, it is recognized by its characteristic, reddish-brown, tabular crystals forming rosettes on a typical rock matrix from Krupka. ## Distinguishing from Similar Minerals It can be confused with other minerals from the tsumcorite group, such as lotharmeyerite (lighter, often orange), tsumcorite (usually green), or gartrellite. Visual differentiation without advanced analytical methods is practically impossible. Key is the analysis of chemical composition, which will show the dominance of manganese over other metals. ## Crystal Forms It forms very small, flattened, tabular crystals, often with a hexagonal or rhombic outline. These crystals combine into radial, fan-shaped, or rosette-like aggregates.

Geological environment

## Genesis It is a secondary mineral, formed in the oxidation zones (iron caps) of polymetallic ore deposits rich in arsenic. It forms as a result of the weathering of primary arsenides and sulfides in the presence of solutions rich in manganese and calcium. ## Mineral Associations It most commonly co-occurs with quartz, hematite, goethite, arsenosiderite, pitticite, pharmacosiderite, scorodite, and other minerals from the tsumcorite group. ## Localities The type and main locality, from which most known specimens originate, is the historic Krupka mine in the Ore Mountains (Krušné Hory) in the Czech Republic. Its occurrence has also been reported in mines in Saxony (Germany), which are in the same geological formation as Krupka.

Rarity

Very rare

For collectors

## Quality Criteria The quality of a manganlotharmeyerite specimen is assessed based on the richness and definition of the crystals in the aggregate. The most desirable specimens are those with clearly formed, undamaged rosettes of an intense, reddish-brown color, contrasting with a light quartz matrix. The size of the aggregates, rather than individual crystals, is important. Due to the nature of the mineral, it is of interest exclusively to specialized collectors of microscopic minerals ("micromounters"). ## Popular Localities The only significant source of collectible specimens is the Krupka mine in the Czech Republic. Specimens from this locality are the standard for this mineral.

Care and storage

## Cleaning Due to the extreme brittleness and small size of the crystals, mechanical cleaning is not recommended. If absolutely necessary, compressed air can be used from a distance, or it can be carefully rinsed with distilled water and then thoroughly dried. ## What to Avoid Avoid contact with acids and other chemicals that can damage arsenates. The mineral is brittle, so avoid shocks, ultrasound, and any mechanical pressure. It should not be heated. ## Storage Specimens should be stored in stable conditions, in sealed "micromount" boxes, to protect them from dust, moisture, and mechanical damage. It is best to display them under a microscope.

Sources

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