Miharaite

Chemical formula: Pb₂+Cu₁+₄Fe₃+Bi₃+S₂-₆

Miharaite is a rare sulfide of lead, copper, iron, and bismuth, forming metallic grains intergrown with other minerals.

## Characteristics Miharaite is a very rare, complex sulfide (sulfosalt) of lead, copper, iron, and bismuth. It occurs as small, anhedral (irregularly shaped) grains, usually not exceeding 0.3 mm in size. It is most often observed as inclusions in bornite or chalcopyrite. It has a metallic luster and a steel-gray to grayish-black color. ## Physical Properties This mineral is characterized by a metallic luster and is opaque. Its Mohs hardness is estimated at 3.5 to 4. The density calculated based on its chemical formula and unit cell parameters is 5.45 g/cm³. ## Colors and Varieties Under a microscope in reflected light, its color is described as creamy yellow with a pinkish tint. No varieties are known. ## History and Name The mineral's name comes from its discovery locality – the Mihara mine in Okayama Prefecture, Japan. It was first described in 1978 by Japanese mineralogists A. Sugaki, A. Kitakaze, and G. Yamamoto. It was approved as a new mineral by the International Mineralogical Association (IMA) in the same year. ## Applications Due to its extreme rarity and occurrence as microscopic grains, miharaite has no industrial applications and is solely an object of scientific interest and for specialized collectors of rare minerals.

Properties

Mohs hardness: 3.5-4
Luster: Metallic
Streak: Black
Density: 5.45
Cleavage: None
Fracture: Uneven
Transparency: Opaque
Crystal system: Orthorhombic

Diagnostic features

## Identification Identification of miharaite is possible almost exclusively using advanced laboratory techniques, such as electron microprobe chemical analysis (EDS/WDS) and X-ray diffraction (XRD). Visually, in the form of microscopic grains with a metallic luster, it is practically impossible to distinguish from other sulfides and sulfosalts. ## Distinguishing from Similar Minerals Under a microscope, it can be confused with many other bismuth sulfosalts, such as wittichenite, emplectite, or aikinite. Definitive distinction requires chemical analysis. It often occurs intergrown with bornite, chalcopyrite, and galena, which further complicates identification. ## Crystal Forms Miharaite forms only small, irregularly shaped (anhedral) grains and aggregates. No euhedral (well-formed) crystals have been observed.

Geological environment

## Genesis Miharaite is a mineral of hydrothermal origin. It forms in the final stages of crystallization in skarn deposits, which develop at the contact of carbonate rocks (limestones) with intrusions of magmatic rocks, such as granite or granodiorite. It crystallizes at relatively high temperatures. ## Mineral Associations This mineral most often occurs in paragenesis with bornite, chalcopyrite, galena, sphalerite, wittichenite, emplectite, native bismuth, and hematite. ## Localities Apart from the type locality, the Mihara mine in Japan, its occurrence has been confirmed in only a few other places worldwide. These include, among others, the Hemlo deposit in Ontario (Canada) and the Băița Bihor mine in Romania. Each of these sites is known for the occurrence of complex sulfide and sulfosalt parageneses.

Rarity

Very rare

For collectors

## Quality Criteria The quality of a miharaite specimen is determined solely by its confirmed presence and identifiability. Since the mineral occurs as microscopic grains, specimens most often take the form of polished sections, where the area with miharaite is marked. The collector's value is purely scientific and depends on the quality of the confirming analysis and the richness of the mineral association on the sample. ## Popular Localities The only source of specimens of collector's significance is the type locality – the Mihara mine in Japan. Specimens from other localities are extremely rare and are mainly found in scientific institutions.

Care and storage

## Cleaning Specimens containing microscopic miharaite, most often in the form of polished sections, should be cleaned only with a dry, soft microfiber cloth or compressed air to remove dust. Any contact with water and chemicals should be avoided. ## What to Avoid Contact with water, acids, detergents, and other chemicals that can react with sulfides, leading to their oxidation and destruction, must be absolutely avoided. The mineral is sensitive to moisture and atmospheric changes, which can cause its slow decomposition. It should be protected from high temperatures. ## Storage Specimens containing miharaite, especially polished sections, should be stored in a dry place, preferably in a sealed, closed "perky box" with a desiccant. Protect from direct sunlight and dust.

Sources

IMA Mineral List (CNMNC)