Tamaite

Chemical formula: (Ca,K,Na)<sub>x</sub>Mn<sup>2+</sup><sub>6</sub>(Si,Al)<sub>10</sub>O<sub>24</sub>(OH)<sub>4</sub>·nH<sub>2</sub>O (x = 1-2; n = 7-11)

Tamaite is a very rare, brown silicate mineral, forming microscopic, bladed crystals, discovered in Japan.

## Characteristics Tamaite is a hydrated calcium, potassium, sodium, manganese, and aluminum silicate, belonging to a group of minerals transitional between micas and zeolites. It occurs as extremely small, bladed or tabular crystals, which rarely exceed 0.1 mm in length. These crystals form rosette-like or radial aggregates, as well as thin coatings and veinlets within the host rock. Due to the microscopic size of the crystals, its visual characteristics are difficult to assess without specialized equipment. ## Physical Properties Tamaite crystals exhibit a vitreous to pearly luster on cleavage surfaces. They are transparent to translucent. The Mohs hardness is approximately 2.5, and the density has been calculated at 2.61 g/cm³. This mineral is characterized by perfect cleavage in one direction. ## Colors and Varieties Tamaite has a color ranging from light brown to brown. No varieties have been distinguished. ## History and Name The mineral was discovered in the Shiromaru mine in Okutama, Tokyo Metropolis, Japan. It was described and approved by the International Mineralogical Association (IMA) in 1998. The name comes from the Tama region, where the discovery site is located (Okutama, meaning "deep Tama"). ## Applications Due to its extreme rarity and microscopic size, tamaite has no industrial applications. It is solely an object of scientific interest and a collector's item for specialized micromineral collectors.

Properties

Mohs hardness
2.5
Luster
Vitreous to Pearly
Streak
Pale brown
Density
2.61
Cleavage
Perfect on {001}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of tamaite is possible almost exclusively through advanced analytical methods, such as X-ray diffraction (XRD) and chemical analysis (EDS/WDS). Visually, in a typical occurrence, it can be suspected based on brown, rosette-like aggregates of microscopic crystals in association with other manganese minerals. ## Differentiation from Similar Minerals It can be confused with other fine-grained manganese minerals, such as ganophyllite, which has a similar appearance and occurs in similar parageneses. Differentiation requires specialized laboratory analysis. ## Crystal Forms It forms very small, bladed or thin-tabular crystals, elongated in one direction. These crystals combine into radial or rosette-like aggregates, and also form fibrous clusters and thin veinlets.

Geological environment

## Genesis This mineral forms as a result of low-temperature hydrothermal processes acting on manganese deposits interbedded in siliceous formations (cherts). It occurs in veinlets cutting through these rocks. ## Mineral Associations It co-occurs with minerals such as ganophyllite, rhodochrosite, quartz, tephroite, alabandite, galena, and pyrite. ## Localities The only confirmed locality of tamaite in the world is its type locality – the Shiromaru mine, Okutama, Tokyo, Japan.

Rarity

Extremely rare

For collectors

## Quality Criteria As a micromineral, the collector's value of tamaite depends on the abundance of its occurrence on the rock matrix, the size and development of aggregates (preferably radial or rosette-like), and the aesthetic contrast with other associated minerals. Any specimen with visible crystals, even under a microscope, is considered valuable. ## Popular Localities All collector material comes from a single location in the world: the Shiromaru mine in Japan. Specimens from this locality are highly sought after by collectors specializing in rare minerals and micromounts.

Care and storage

## Cleaning Specimens containing tamaite should generally not be wet-cleaned due to their delicacy and potential reactivity. If absolutely necessary, compressed air (from a safe distance) can be used to remove dust. Contact with water should be avoided. ## What to Avoid All chemicals, acids, and detergents should be strictly avoided. The mineral is soft and susceptible to mechanical damage. It should not be heated or exposed to prolonged moisture. ## Storage Tamaite specimens, as microminerals, should be stored in specialized "micromount" boxes that protect them from dust, shocks, and mechanical damage. They should be kept in stable room conditions, away from sources of moisture.

Sources

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