Kamiokite

Chemical formula: Fe²⁺₂Mo⁴⁺₃O₈

Kamiokite is a rare, black iron and molybdenum oxide with a metallic luster, forming hexagonal crystals.

## Characteristics Kamiokite is a rare mineral from the oxide group, composed of iron and molybdenum. It occurs as small, tabular or platy crystals with a hexagonal outline, reaching sizes up to 0.5 mm. It also forms granular aggregates. Its color is black, and on fresh surfaces, it exhibits a strong, metallic luster. ## Physical Properties This mineral is opaque and relatively brittle. Its Mohs hardness is approximately 4.5, and its density is significant – 5.96 g/cm³. Under a microscope in reflected light, it may show a gray color with an olive tint. ## History and Name Kamiokite was first described in 1975 by A. Sasaki, S. Yui, and M. Yamaguchi. Its name comes from its discovery location – the Kamioka mine in Gifu Prefecture, Japan. It is a type locality mineral for this location. ## Applications Due to its extreme rarity, kamiokite has no industrial applications. It is solely an object of scientific interest and is valued by specialized collectors of rare minerals.

Properties

Mohs hardness: 4.5
Luster: Metallic
Streak: Black
Density: 5.96
Cleavage: on [0001]
Transparency: Opaque
Crystal system: Hexagonal

Diagnostic features

## Identification Kamiokite can be identified by its black color, strong metallic luster, and characteristic small hexagonal crystals. Its high density is also a helpful feature. The streak is black. Its occurrence in association with molybdenite and seynite in skarns is a key indicator. ## Distinguishing from Similar Minerals It can be confused with molybdenite, with which it often co-occurs. However, molybdenite is much softer (hardness 1-1.5), has perfect cleavage in one direction, and leaves a gray, greasy-feeling streak. Other black minerals with a metallic luster, such as magnetite, differ from kamiokite in crystal form and magnetic properties. ## Crystal Forms It most commonly forms small, hexagonal, tabular or platy crystals. It also occurs as granular aggregates, intergrown with other minerals, mainly quartz.

Geological environment

## Genesis Kamiokite is a hydrothermal mineral. It forms in skarns, which are metamorphic rocks created at the contact of a magmatic intrusion (in this case, granite) with iron-rich sedimentary rocks. Its crystallization occurs at relatively high temperatures. ## Mineral Associations This mineral most commonly co-occurs with molybdenite, seynite, pyrite, pyrrhotite, magnetite, sphalerite, galena, and quartz. ## Localities The most important and classic occurrence of kamiokite is its type locality – the Tochibora deposit in the Kamioka mine, Gifu Prefecture, Japan. This is the only confirmed and well-documented locality for this mineral in the world.

Rarity

Very rare

For collectors

## Quality Criteria The most valuable specimens for collectors are those with well-formed, sharp, hexagonal crystals exhibiting a strong, untarnished metallic luster. Specimens where kamiokite is clearly visible against a contrasting background, such as white quartz, are also highly prized. Due to the small size of the crystals, even millimeter-sized specimens are considered valuable. ## Popular Localities The only source of collector specimens is the Kamioka mine in Japan. Material from this locality is extremely difficult to acquire and appears on the market very rarely.

Care and storage

## Cleaning Kamiokite specimens should be cleaned very carefully, using only a soft brush to remove dust. Due to its brittleness and rarity, wet cleaning and ultrasonic cleaners should be avoided. ## What to Avoid This mineral is susceptible to oxidation. It should be protected from moisture, chemicals, and sudden temperature changes. Prolonged exposure to humid air can lead to dulling of its metallic luster. ## Storage It is recommended to store kamiokite specimens in stable conditions, preferably in sealed, dry containers (e.g., boxes with membranes or boxes with desiccant). Direct contact with other minerals should be avoided to prevent mechanical damage.