Alumino-magnesiotaramite

Chemical formula: Na₂CaMg₃Al₂(Si₆Al₂)O₂₂(OH)₂

Alumino-magnesiotaramite is an extremely rare mineral from the amphibole group, characterized by a complex chemical composition and known from only a few localities worldwide.

## Characteristics Alumino-magnesiotaramite is a complex silicate from the amphibole supergroup, belonging to the calcic-sodic amphibole subgroup. It forms very small, prismatic crystals, rarely exceeding 1 mm in length. It typically occurs as radial or fibrous aggregates. Due to the microscopic size of its crystals, its visual characteristics are difficult to assess without specialized equipment. It is a rock-forming mineral under very specific metamorphic conditions. ## Physical Properties Crystals have a hardness of 6 on the Mohs scale and a vitreous luster. The calculated density is 3.23 g/cm³. The mineral is usually translucent on thin edges to opaque. It exhibits typical amphibole cleavage. ## Colors and Varieties Alumino-magnesiotaramite is black, and its streak is grayish-green. No color or commercial varieties are distinguished, which is typical for such rare microscopic minerals. ## History and Name The mineral was first described in 2006 by a group of researchers led by Roberta Oberti. Its name directly refers to its chemical composition – high aluminum (alumino) and magnesium (magnesio) content – and its structural kinship with taramite, another mineral from the amphibole group. The type locality is the Vápenný vrch quarry near the town of Třinec in the Czech Republic. ## Uses As an extremely rare mineral occurring in microscopic crystals, alumino-magnesiotaramite has no commercial or industrial applications. Its significance is purely scientific and it is of interest to specialized collectors of microscopic minerals (so-called "micromounts").

Properties

Mohs hardness: 6
Luster: Vitreous
Streak: Greyish green
Density: 3.23
Cleavage: Good on {110}
Fracture: Uneven
Transparency: Translucent to Opaque
Crystal system: Monoclinic

Diagnostic features

## Identification Amateur identification of alumino-magnesiotaramite is impossible. It is a black, microscopic prismatic mineral that is visually indistinguishable from dozens of other amphiboles. Certain identification requires advanced analytical techniques, such as X-ray microanalysis (EDS/WDS) to determine chemical composition and X-ray diffraction (XRD) to confirm crystal structure. ## Distinguishing from Similar Minerals Alumino-magnesiotaramite is visually indistinguishable from other black amphiboles, such as hornblende, arfvedsonite, ferro-pargasite, or other minerals from the taramite series. The differences lie solely in the subtle proportions of sodium, calcium, magnesium, iron, and aluminum in the structure, which is impossible to verify without specialized equipment. ## Crystal Forms It forms columnar or prismatic crystals, usually no longer than 1 mm. They often occur as radial or tangled aggregates. Crystals are typically terminated by simple faces.

Geological environment

## Genesis This mineral forms under contact metamorphic conditions. In the type locality (Czech Republic), it occurs in calc-silicate lenses within teschenites – an alkaline igneous rock. Its formation is associated with metasomatic interaction with calcium- and magnesium-rich rocks at relatively high temperatures. ## Mineral Associations It most commonly co-occurs with minerals such as grossular (hessonite variety), clinochlore, titanite, prehnite, apatite, and diopside. ## Localities Alumino-magnesiotaramite is an extremely rare mineral. Apart from the type locality – the Vápenný vrch quarry in the Czech Republic – its occurrence has been confirmed in only a few other places worldwide, in similar geological environments.

Rarity

Extremely rare

For collectors

## Quality Criteria For such a rare microscopic mineral, the most important criterion for value is certainty of identification, preferably confirmed by chemical analysis. A collector's specimen should consist of well-formed, undamaged crystals, even if they are very small. The presence of associated minerals, typical for a given locality, enhances its attractiveness. Crystal size, although always desirable, is secondary to quality and confirmation of authenticity. ## Popular Localities The only source of specimens available on the collector's market is its type locality: Vápenný vrch quarry, Třinec, Moravian-Silesian Region, Czech Republic.

Care and storage

## Cleaning Specimens should only be cleaned with distilled water, using a very soft brush to remove dust. Due to the small size of the crystals and their fragility, utmost care must be taken. Ultrasonic cleaners are absolutely not recommended, as they can destroy delicate aggregates. ## What to Avoid The mineral should be protected from contact with acids and other chemicals. It is susceptible to mechanical damage due to its cleavage, so impacts and shocks should be avoided. Sudden temperature changes can also be harmful. ## Storage The safest storage method is to place the specimen in a closed, padded "micromount" box, which protects it from dust, light, and mechanical damage. Each specimen should be precisely labeled with its name and locality.

Sources

IMA Mineral List (CNMNC)