Mikasaite

Chemical formula: Fe³⁺₂(S⁶⁺O₄)₃

Mikasaite is a rare iron(III) sulfate, forming small, prismatic, yellow crystals, found in a single locality worldwide.

## Characteristics Mikasaite is a hydrated iron(III) sulfate, occurring as very small, prismatic crystals that rarely exceed 0.3 mm in length. It forms aggregates of grains or appears as single, tabular crystals. It is a secondary mineral, formed under specific conditions of sulfide rock weathering. ## Physical Properties Mikasaite crystals exhibit a vitreous luster. Due to the small size of the crystals, precise determination of hardness and density is difficult; the density calculated based on the formula and cell parameters is 3.33 g/cm³. The mineral is transparent to translucent. ## Colors and Varieties Mikasaite has a characteristic, bright yellow color. No varieties have been described. ## History and Name The mineral's name comes from the city of Mikasa in Hokkaido Prefecture, Japan, near which its only known locality, the Okumanza mine, is located. The mineral was approved by the IMA in 1993, and its description was published in 1994. The authors of the description were H. Miura, M. Imafuku, and T. Yasuda. ## Uses Due to its extreme rarity and microscopic size, mikasaite has no industrial applications. It is solely an object of scientific interest and a collector's item for specialized rare mineral collectors.

Properties

Mohs hardness
2
Color
White to light brown
Luster
Dull
Streak
White to light brown
Density
0
Cleavage
None
Fracture
Uneven
Transparency
Transparent to Translucent
Crystal system
Trigonal

Diagnostic features

## Identification Identifying mikasaite under amateur conditions is practically impossible due to the microscopic size of the crystals. Identification requires advanced analytical methods, such as X-ray diffraction (XRD) and chemical analysis (EDS/WDS). It is distinguished by its bright yellow color and co-occurrence with other sulfates. ## Distinguishing from Similar Minerals It can be confused with other secondary iron sulfates, such as jarosite, copiapite, or metavoltine, which have similar color and genesis. Definitive differentiation is possible only through structural and chemical analysis. ## Crystal Forms Mikasaite forms small, prismatic or tabular crystals with a hexagonal cross-section. They occur as individual specimens or in granular aggregates.

Geological environment

## Genesis Mikasaite is a secondary mineral, formed as a result of weathering (oxidation) of sulfide deposits in a low-humidity environment. It forms in the oxidation zones of ore deposits, often in mines. ## Mineral Associations At the type locality (Okumanza mine), it co-occurs with metavoltine, jarosite, gypsum, pyrite, quartz, and clay minerals. ## Localities The only confirmed occurrence of mikasaite in the world is its type locality: the Okumanza mine, near Mikasa city, on Hokkaido island, Japan.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a specimen depends solely on the quantity and visibility of mikasaite microcrystals on the rock matrix. The best specimens are those where the yellow crystals form rich, well-visible aggregates under a microscope, contrasting with the substrate. The size of individual crystals, even if it is a fraction of a millimeter, is crucial. ## Popular Localities The only source of specimens is the Okumanza mine in Japan. Material from this locality is extremely difficult to obtain and appears on the collector's market sporadically.

Care and storage

## Cleaning Mikasaite specimens are extremely delicate and sensitive. Mechanical cleaning and contact with water should be avoided. If cleaning is absolutely necessary, compressed air (from a safe distance) can be used to remove dust. ## What to Avoid The mineral is likely soluble in water and acids. Contact with any liquids must be strictly avoided. It should be protected from moisture, high temperatures, and direct sunlight, which can cause dehydration and disintegration. ## Storage Specimens should be stored in a sealed, dry container (such as a "perky box") away from sources of moisture and light. Due to its fragility, vibrations and shocks should be avoided.

External references

Sources

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