Magnesiobermanite

Chemical formula: MgMn<sup>3+</sup><sub>2</sub>(PO<sub>4</sub>)<sub>2</sub>(OH)<sub>2</sub>·4H<sub>2</sub>O

Magnesiobermantite is a rare hydrated magnesium and manganese phosphate, forming microscopic, reddish-brown, platy crystals.

## Characteristics Magnesiobermantite is a very rare mineral from the phosphate group. It occurs as very small, platy or bladed crystals, rarely exceeding 0.5 mm in length. These crystals often form rosette-like or radial aggregates. Due to its microscopic size, it is a mineral primarily of interest to specialized collectors (micromounters). ## Physical Properties The mineral is characterized by a vitreous luster and is transparent to translucent. Its Mohs hardness is approximately 4, and its density is close to 2.58 g/cm³. It exhibits perfect cleavage in one direction. ## Colors and Varieties The typical color of magnesiobermantite is reddish-brown. No varieties have been distinguished. ## History and Name The mineral's name refers to its chemical composition – the presence of magnesium (magnesio) – and its structural similarity to bermanite. It was approved as a new mineral by the International Mineralogical Association (IMA) in 1983. It was described by Pete J. Dunn, Donald R. Peacor, Willard L. Roberts, and Thomas J. Campbell based on samples from the Tip Top mine in Custer County, South Dakota, USA.

Properties

Mohs hardness
4
Luster
Vitreous
Streak
Light brown
Density
2.58
Cleavage
Perfect on {010}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Amateur identification of magnesiobermantite is practically impossible due to the microscopic size of the crystals. It requires advanced analytical methods, such as X-ray diffraction (XRD) and energy-dispersive spectroscopy (EDS) to confirm its chemical composition. Visually, it can be suspected based on its reddish-brown color, platy crystal habit, and co-occurrence with other rare phosphates in pegmatites. ## Distinguishing from Similar Minerals It can be confused with other microscopic, reddish phosphates, such as bermanite or jahnsite. Bermanite has a very similar appearance, but magnesiobermantite is distinguished by the dominance of magnesium over manganese in a specific structural position, which cannot be determined without chemical analysis. ## Crystal Forms The crystals are very small, usually platy or bladed, flattened parallel to the {010} plane. They often form radial or rosette-like aggregates on the surface of other minerals.

Geological environment

## Genesis Magnesiobermantite is a secondary mineral, formed in complex granitic pegmatites. It forms as a result of hydrothermal processes or weathering, which lead to the alteration of primary phosphate minerals, such as triplite. ## Mineral Associations It co-occurs with other phosphate minerals, such as rockbridgeite, strengite, phosphosiderite, hureaulite, tavorite, barbosalite, leucophosphite, triplite, as well as quartz and albite. ## Localities The most important and type locality (località tipo) is the Tip Top mine in Custer County, South Dakota, USA. This is the only confirmed and well-documented locality for this mineral worldwide.

Rarity

Very rare

For collectors

## Quality Criteria For micromineral collectors (micromounters), the most valuable specimens are those with well-formed, sharp crystals forming aesthetic, rosette-like aggregates. Contrast with the matrix mineral and the presence of rare associated minerals are also important. The size of individual crystals, even if sub-millimeter, matters – the larger, the more valuable. ## Popular Localities The only source of collectible specimens is the Tip Top mine in South Dakota, USA. All specimens available on the market originate from this single locality.

Care and storage

## Cleaning Specimens should only be cleaned with compressed air to remove dust. Due to the extreme delicacy and small size of the crystals, any mechanical contact, including with water or brushes, should be avoided. ## What to Avoid Avoid contact with water, chemicals, ultrasound, and sudden temperature changes. The crystals are very brittle and susceptible to mechanical damage. ## Storage Magnesiobermantite specimens should be stored exclusively in specialized micromount boxes to protect them from dust, shocks, and damage. Avoid exposure to direct sunlight, although its effect on the mineral's stability is not known.

Sources

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