Cadmoindite
Chemical formula: Cd<sup>2+</sup>In<sup>3+</sup><sub>2</sub>S<sup>2-</sup><sub>4</sub>
Cadmoindite is an extremely rare cadmium and indium sulfide, forming small, black, metallic crystals in volcanic fumaroles.
Description
## Characteristics Cadmoindite is a sulfide mineral, chemically classified as cadmium and indium sulfide (CdIn₂S₄). It forms very small, but well-formed octahedral crystals, typically not exceeding 0.5 mm in size. It also occurs as granular aggregates. Its color is uniformly black, and its appearance is opaque. ## Physical Properties This mineral is characterized by a strong metallic luster. Its density is calculated to be 4.43 g/cm³. Due to the small size of the crystals, other physical properties, such as hardness, are difficult to determine precisely. ## Colors and Varieties Cadmoindite is a monochromatic mineral, occurring exclusively in black. No varieties are distinguished. ## History and Name The name cadmoindite refers directly to its chemical composition – the presence of cadmium and indium. The mineral was first described in 2004 by a team of mineralogists led by N. N. Mozgova based on material collected from the Kudryavy volcano. ## Applications Due to its extreme rarity, cadmoindite has no industrial applications and is solely an object of scientific interest and a prize for specialized collectors of rare minerals.
Diagnostic features
## Identification Identification of cadmoindite is based on its characteristic appearance – small, black, metallic crystals with an octahedral shape. A key diagnostic feature is its unique occurrence environment (volcanic fumaroles) and paragenesis with other rare minerals. ## Distinguishing from Similar Minerals It can be confused with other small, black metallic minerals. Certain differentiation from similar sulfides requires advanced analytical methods, such as chemical composition analysis (EDS). However, the geological context is very helpful. ## Crystal Forms It occurs in the form of sharply terminated, regular octahedra and as granular aggregates.
Geological environment
## Genesis Cadmoindite forms under very specific conditions as a sublimation product from hot volcanic gases (fumaroles) at temperatures exceeding 600°C. ## Mineral Associations It co-occurs with other fumarolic minerals such as pyrite, wurtzite, greenockite, kudryavtsevite, and rhenium sulfide. ## Localities The only confirmed locality of cadmoindite in the world is its type locality – Kudryavy volcano on Iturup Island (Kuril Islands, Russia).
Rarity
Extremely rare
Collector aspects
## Quality Criteria Specimens with well-formed, sharp octahedral crystals, set on a contrasting matrix, are most highly valued. Co-occurrence with other rare minerals from this locality enhances its attractiveness. ## Popular Localities All collectible specimens come from a single location in the world – Kudryavy volcano in the Kuril Islands.
Care and storage
## Cleaning Specimens should only be cleaned with compressed air or a very soft brush. Avoid contact with water and any chemical agents. ## What to Avoid As a sulfide, cadmoindite can be sensitive to moisture and oxidation. Avoid contact with acids, detergents, and other chemicals. It should not be heated or exposed to sudden temperature changes. ## Storage It is recommended to store specimens in stable conditions, in closed, dry containers (e.g., "membrane box" type), away from light and contaminants. Protect from dust and moisture.