Takanelite

Chemical formula: (Mn₂+,Ca)₂xMn₄+₁-xO₂·₀.₇H₂O

Takanelite is a rare hydrated manganese oxide, forming black, earthy or finely crystalline aggregates with a metallic luster.

## Characteristics Takanelite is a mineral from the oxide group, chemically classified as a hydrated manganese oxide with calcium. It typically occurs in massive, earthy, or sooty aggregates and crusts. It rarely forms discernible crystals, which are microscopic, hexagonal plates. Its surface has a characteristic luster, from metallic to dull, depending on the compactness of the aggregate. ## Physical Properties This mineral is opaque and relatively soft, with a hardness of about 5 on the Mohs scale. Its density ranges from 3.4 to 3.6 g/cm³. Despite occurring in massive aggregates, it has excellent cleavage in one direction, which is rarely observed in practice due to the finely crystalline nature of the specimens. ## Colors and Varieties Takanelite is a mineral of uniform, black color. Sometimes its streak is brownish-black. No color varieties or trade names are distinguished for it. ## History and Name The mineral's name comes from its discovery locality – the Takané mine in Iwate Prefecture, Japan. It was described and recognized as a new mineral in 1970 by Japanese mineralogists Matsuo Nambu and Katsutoshi Tanida. ## Applications Due to its rarity and inconspicuous appearance, takanelite has no industrial application. It is solely an object of scientific and collecting interest, especially for those specializing in mineral systematics or collecting specimens from type localities.

Properties

Mohs hardness: 5
Luster: Metallic to Dull
Streak: Black to brownish-black
Density: 3.4-3.6
Cleavage: Perfect on {0001}
Fracture: Uneven
Transparency: Opaque
Crystal system: Hexagonal

Diagnostic features

## Identification Characteristic features of takanelite include its black color, black or brownish-black streak, and metallic to dull luster. Its occurrence environment is crucial – oxidation zones of manganese deposits, in association with other manganese minerals. ## Distinguishing from Similar Minerals Macroscopic differentiation of takanelite from other black manganese oxides (so-called "psilomelanes"), such as pyrolusite, birnessite, cryptomelane, or todorokite, is practically impossible without advanced laboratory analyses, e.g., X-ray diffraction (XRD). Many specimens visually identified as "manganese oxides" may actually be a mixture of several different minerals. ## Crystal Forms Most commonly, it forms massive, compact, earthy, sooty, or crusty aggregates. Microscopic crystals in the form of hexagonal plates are very rarely observed.

Geological environment

## Genesis Takanelite is a secondary mineral. It forms in oxidation (weathering) zones of hydrothermal and sedimentary manganese deposits. It is formed as a result of the alteration of primary manganese minerals, mainly rhodochrosite. ## Mineral Associations It most often co-occurs with other manganese minerals, such as rhodochrosite, pyrolusite, birnessite, nsutite, cryptomelane, and todorokite. ## Localities The most important and classic localities for this mineral are in Japan, in the Takané (type locality) and Yamato mines. It is also known from manganese deposits in Hotazel and Kuruman in South Africa (Kalahari basin) and from single occurrences in Australia and the USA.

Rarity

Rare

For collectors

## Quality Criteria For collectors, specimens from the type locality in Japan are the most valuable. The quality of a specimen is enhanced by the presence of visible, even microscopic, hexagonal crystals. Rich aggregates of takanelite or its crusts on a contrasting substrate, such as pink rhodochrosite, are also attractive. ## Popular Localities The most prized specimens by specialist collectors come from the Takané mine in Iwate Prefecture, Japan.

Care and storage

## Cleaning Takanelite specimens should be cleaned very carefully, preferably dry, using a soft brush to remove dust. If the specimen is compact and does not crumble, it can be rinsed with distilled water and then thoroughly dried. Ultrasonic cleaners should be avoided. ## What to Avoid The mineral is sensitive to acids, which can damage or completely dissolve it. All contact with chemicals should be avoided. Earthy and brittle specimens are susceptible to mechanical damage and abrasion. ## Storage It is recommended to store takanelite in separate, closed display boxes to protect it from dust and mechanical damage, especially if it is in the form of fragile aggregates. It is stable under standard lighting and temperature conditions.

Sources

IMA Mineral List (CNMNC)