Iyoite

Chemical formula: Mn<sup>2+</sup>Cu<sup>2+</sup>Cl(OH)<sub>3</sub>

Iyoite is an extremely rare copper and manganese hydroxychloride, forming characteristic rosette-like aggregates of pale blue crystals.

## Characteristics Iyoite is a mineral from the hydroxychloride group, chemically classified as a copper and manganese hydroxychloride. It occurs as small, tabular or platy crystals, which almost always form spherical or rosette-like aggregates. Its color is usually pale green to pale bluish-green. Due to its rarity and small crystal size, it is a mineral known mainly in scientific and specialized circles. ## Physical Properties Iyoite crystals exhibit a vitreous luster and are translucent. The calculated density for this mineral is approximately 3.55 g/cm³. The hardness has not yet been precisely determined. The mineral is characterized by perfect cleavage in one plane. ## Colors and Varieties This mineral is color-uniform and occurs in shades from pale green to pale bluish-green. No color or commercial varieties have been distinguished. ## History and Name Iyoite was officially recognized as a new mineral species by the International Mineralogical Association (IMA) in 2013. Its name comes from the former Iyo Province in Japan, where its only known occurrence, the Ohku mine, is located. It was discovered by Japanese mineralogists, including Daisuke Nishio-Hamane, who is the main author of its description. ## Applications Due to its extreme rarity and occurrence in the form of small aggregates, iyoite has no industrial application. It is solely an object of scientific interest and a valuable acquisition for specialized mineral collectors.

Properties

Luster
Vitreous
Streak
Pale green
Density
3.55
Cleavage
Perfect on {001}
Transparency
Translucent
Crystal system
Orthorhombic

Diagnostic features

## Identification The characteristic feature of iyoite is its unique, rosette-like or spherical aggregates composed of small, platy crystals of pale green or pale bluish color. Its extreme rarity and occurrence in only one location worldwide are key diagnostic indicators. However, definitive identification requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical microanalysis (EDS). ## Distinguishing from Similar Minerals Iyoite can be confused with other secondary copper minerals of similar color, such as calcioatacamite, paratacamite, or brightly colored malachite. However, it is distinguished by its specific aggregate form (rosettes), perfect cleavage, and unique geochemical environment (co-occurrence with manganese minerals). In practice, due to its origin from only one locality, confusion is unlikely if the specimen's locality is known. ## Crystal Forms Iyoite forms thin, tabular or platy crystals with a hexagonal outline. These crystals almost always occur as radial, spherical, or rosette-like aggregates, reaching up to several millimeters in diameter.

Geological environment

## Genesis Iyoite is a secondary mineral that forms in the oxidation zone of copper and manganese ore deposits. Its formation is associated with the weathering processes of primary ore minerals in a chlorine-rich environment, the source of which could have been seawater or other brines. ## Mineral Associations This mineral occurs in association with other secondary minerals. It is most commonly found in association with calcioatacamite, goethite, and quartz. ## Localities The only confirmed and described occurrence of iyoite in the world is its type locality – the Ohku mine, in Ehime Prefecture (formerly Iyo Province) on Shikoku Island, Japan.

Rarity

Extremely rare

For collectors

## Quality Criteria The most highly prized iyoite specimens are those with well-formed, distinct rosette-like aggregates of intense, pale bluish-green color. The size of the aggregates themselves and their contrasting placement on the rock matrix are also of great importance. Specimens with visible associated minerals, such as calcioatacamite, are also highly valued. ## Popular Localities The only source of iyoite specimens is the Ohku mine in Japan. Material from this locality is extremely difficult to acquire and appears on the collector's market sporadically.

Care and storage

## Cleaning Iyoite specimens should only be dry-cleaned, using a soft brush to remove dust. Due to its chemical composition (chloride), contact with water, and especially with chemical solutions, is absolutely inadvisable and can lead to its permanent damage or decomposition. ## What to Avoid Avoid contact with water, acids, detergents, and all chemical agents. This mineral may be sensitive to sudden temperature changes and high humidity. It should not be cleaned in ultrasonic or steam cleaners. ## Storage It is recommended to store iyoite specimens in a dry place, preferably in a tightly sealed container (e.g., a "perky box"), to isolate it from humidity fluctuations. Protect from direct sunlight, which could cause its color to change over time.

External references

Sources

Read more