Kodamaite

Chemical formula: Na₃(Ca₅Na)Si₁₆O₃₆(OH)₄F₂·(₁₄-x)H₂O (x ~ ₅)

Kodamaite is an extremely rare, colorless silicate mineral, discovered in Japan, with a complex chemical structure containing sodium, calcium, and fluorine.

## Characteristics Kodamaite is a mineral with a complex structure, belonging to the layered silicates. It forms very small, colorless, lath-like crystals, which usually occur as radial or tangled aggregates. Due to the small size of the crystals (typically less than 1 mm), its visual features are difficult to observe without specialized equipment, such as a microscope. ## Physical Properties Kodamaite crystals exhibit a vitreous luster. This mineral is transparent. Its Mohs hardness is approximately 4, and its density is slightly greater than that of quartz, at 2.75 g/cm³. ## Colors and Varieties Kodamaite is colorless. No colored varieties have been described to date. ## History and Name The mineral was officially recognized by the International Mineralogical Association (IMA) in 2019. Its name honors Dr. Kazuo Kodama (born 1956), a Japanese geologist and researcher from Hiroshima University, for his contributions to petrological and geochronological studies of metamorphic rocks in Japan. The discovery was made in the Fuka mine, Okayama Prefecture, Honshu Island. ## Applications Due to its extreme rarity and microscopic size, kodamaite 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: 2-0
Color: tan to creamy-yellow to white in color, less often being colorless, light or dark green, or white.
Luster: Vitreous
Streak: white
Density: 2.16
Cleavage: {001}
Fracture: Uneven
Transparency: Transparent,Translucent
Crystal system: Triclinic

Diagnostic features

## Identification Identification of kodamaite is impossible without advanced laboratory techniques, such as X-ray diffraction (XRD) and chemical analysis (e.g., electron microprobe). In collecting contexts, identification relies solely on trust in a label from a reliable source, confirming previous scientific studies. ## Distinguishing from Similar Minerals Kodamaite can be confused with many other colorless, acicular or lath-like secondary minerals occurring in similar parageneses, such as tobermorite, tacharanite, or jennite. Distinguishing them "by eye" or with simple tests is unfeasible. ## Crystal Forms Kodamaite forms elongated, lath-like crystals with a rectangular cross-section, often flattened. These crystals combine into radial or haphazardly tangled aggregates, forming small clusters on the surface of the host rock.

Geological environment

## Genesis Kodamaite is a secondary mineral, formed as a result of hydrothermal processes occurring within skarns. It forms at low temperatures in veins cutting through calc-silicate rocks, which originated at the contact of magmatic intrusions with carbonate sedimentary rocks (limestones). ## Mineral Associations This mineral occurs in association with other rare skarn minerals. In the type locality (Fuka mine), its co-occurrence with bultfonteinite, scawtite, apophyllite, calcite, and minerals from the tobermorite group has been observed. ## Localities The only confirmed occurrence of kodamaite in the world is its type locality – the Fuka mine, near Takahashi City, Okayama Prefecture (Chūgoku region) on the Japanese island of Honshu.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a kodamaite specimen primarily depends on the richness and aesthetics of the crystal aggregates on the rock matrix. Most valued are specimens with clearly visible, well-formed, radial clusters of colorless crystals, contrasting with the darker host rock. Due to the microscopic nature of the mineral, the quality of the specimen observed under magnification is crucial. ## Popular Localities The only source of kodamaite specimens is the Fuka mine in Japan. Material from this locality is extremely difficult to obtain and appears on the collector's market sporadically.

Care and storage

## Cleaning Kodamaite specimens, typically microscopic crystals on a rock matrix, should not be cleaned mechanically or chemically. Any attempts at cleaning can irreversibly damage the delicate crystals. If dust removal is necessary, a gentle stream of compressed air can be used from a safe distance. ## What to Avoid Avoid contact with any chemicals, including acids and bases. The mineral is sensitive to shocks and mechanical damage. It should not be heated or exposed to rapid temperature changes. ## Storage Kodamaite specimens ("micromounts") should be stored exclusively in specialized, sealed perky boxes, which protect them from dust, moisture, and mechanical damage. They should be kept in stable room conditions, away from direct sunlight and sources of vibration.

External references

https://www.mindat.org/min-53862.html