Taniajacoite

Chemical formula: SrCaMn<sup>3+</sup><sub>2</sub>Si<sub>4</sub>O<sub>11</sub>(OH)<sub>4</sub>·2H<sub>2</sub>O

Taniajacoite is a very rare strontium, calcium, and manganese silicate, forming microscopic, orange-brown, bladed crystals.

## Characteristics Taniajacoite is an extremely rare mineral from the silicate group, chemically classified as a hydrated strontium, calcium, and trivalent manganese silicate. It occurs as very small, bladed or acicular crystals, rarely exceeding 0.2 mm in length. These crystals form radial or tangled aggregates, and their small size means they are primarily visible under a microscope. ## Physical Properties Taniajacoite crystals exhibit a vitreous luster. Due to their microscopic size, most physical properties, such as hardness or density, have not been precisely determined. The mineral is brittle. ## Colors and Varieties This mineral is characterized by a uniform, orange-brown color. No colored varieties or commercial forms have been reported. ## History and Name The name taniajacoite was given in honor of Tânia Jaco Coelho (born 1960), a Brazilian geologist from the University of São Paulo, in recognition of her contributions to the study of manganese deposit geology. The mineral was approved by the International Mineralogical Association (IMA) in 2011 (IMA2011-061). It was discovered in the Wessels Mine in the Republic of South Africa. ## Uses Due to its extreme rarity and microscopic size, taniajacoite has no industrial applications. It is solely an object of scientific interest and a valuable acquisition for specialized collectors of rare minerals (so-called "micromounts").

Properties

Mohs hardness
4
Luster
Vitreous
Streak
Light brown
Density
3.06
Cleavage
Perfect on {010}
Fracture
Uneven
Transparency
Translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Amateur identification of taniajacoite is practically impossible. It requires advanced analytical techniques such as Raman spectroscopy, X-ray diffraction (XRD), and chemical analysis (EDS/WDS) to confirm its composition and structure. A visual characteristic, though insufficient for certain identification, is the occurrence of orange-brown, bladed crystals in radial aggregates. ## Distinguishing from Similar Minerals This mineral can be confused with other rare manganese silicates of similar color and form, such as ruizite or orientite, which also occur in the Kalahari deposits. Definitive differentiation is only possible using laboratory methods. ## Crystal Forms Taniajacoite forms elongated, bladed or acicular crystals, often flattened. These crystals combine into characteristic, radial or chaotically tangled aggregates.

Geological environment

## Genesis Taniajacoite is a hydrothermal mineral. It forms in the late stage of mineralization in manganese deposits, crystallizing in fractures and small rock cavities. Its formation is associated with low-temperature processes occurring in manganese-rich sedimentary rocks of the Hotazel Formation. ## Mineral Associations This mineral co-occurs with other manganese minerals and silicates. It is most commonly associated with sugilite, pectolite, quartz, braunite, hematite, and rare minerals such as ruizite and effenbergerite. ## Localities The only confirmed locality of taniajacoite in the world (type locality) is the Wessels Mine, located in the Hotazel area of the Kalahari Manganese Field, Northern Cape Province, Republic of South Africa.

Rarity

Extremely rare

For collectors

## Quality Criteria For taniajacoite, as a "micromount" mineral, the most important criterion is the quality and richness of the crystal aggregates on the matrix. Specimens with clearly formed, radial clusters of sharply terminated, undamaged crystals are most valued. The color contrast of the orange-brown crystals against a lighter background (e.g., with pectolite or quartz) also enhances the visual appeal of the specimen. ## Popular Localities All taniajacoite specimens available on the collector's market come from its only known locality – the Wessels Mine in South Africa. This is a classic locality for many rare manganese minerals.

Care and storage

## Cleaning Taniajacoite specimens, typically microscopic crystals on matrix, should not be cleaned mechanically or chemically. The safest method for dust removal is to use compressed air from a safe distance. ## What to Avoid Avoid contact with all chemicals, including acids and detergents. Do not subject specimens to ultrasonic cleaning. Due to its brittleness, avoid any impacts and vibrations. ## Storage Specimens should be stored in stable conditions, away from dust and moisture. The best solution is a dedicated "micromount" box, which protects delicate crystals from mechanical damage and contamination.

Sources

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