Erazoite

Chemical formula: Cu<sub>4</sub>SnS<sub>6</sub>

Erazoite is an extremely rare copper-tin sulfide, occurring as black, metallic grains at its only known locality in Chile.

## Characteristics Erazoite is a copper-tin sulfide with a metallic luster and black color. It occurs as very small, anhedral (irregular) or subhedral grains, not exceeding 150 micrometers in size. These grains form aggregates up to 250 micrometers, often intergrown with other sulfides. The mineral is opaque. ## Physical Properties The luster of erazoite is distinctly metallic. Hardness has not been precisely determined. The density calculated based on chemical composition and unit cell parameters is 4.73 g/cm³. ## Colors and Varieties This mineral is uniformly black. No color varieties or commercial varieties are known. ## History and Name Erazoite was officially recognized as a new mineral by the International Mineralogical Association (IMA) in 2012. Its name honors Miguel Ángel Erazo (born 1952), a Chilean mining technician who found and collected the first samples of this mineral, enabling its study. ## Applications Due to its extreme rarity, erazoite has no industrial applications. It is solely an object of scientific interest and a valuable acquisition for advanced systematic collections.

Properties

Luster
Metallic
Streak
Black
Density
4.73
Cleavage
None
Transparency
Opaque
Crystal system
Orthorhombic

Diagnostic features

## Identification Identification of erazoite is impossible without advanced analytical techniques. Under collecting conditions, identification relies on the confirmed locality (El Guanaco mine) and characteristic mineral association. Visually, it is a black, metallic mineral occurring as fine grains. ## Distinguishing from Similar Minerals Erazoite is visually indistinguishable from many other black sulfides with which it co-occurs, such as enargite, luzonite, stannoidite, or covellite. Definitive differentiation requires chemical analysis (e.g., EDS/WDS) to confirm the Cu-Sn-S composition. ## Crystal Forms The mineral forms anhedral (irregular) or subhedral (partially developed) grains, typically of microscopic size. Well-formed, freestanding crystals are not observed.

Geological environment

## Genesis Erazoite forms under hydrothermal conditions, within high-sulfidation epithermal deposits. It is a product of crystallization from solutions rich in copper, tin, and sulfur. ## Mineral Associations This mineral occurs in close association with other sulfides and sulfosalts. It is most commonly found in association with enargite, luzonite, stannoidite, and covellite. ## Localities The only confirmed locality of erazoite in the world (type locality) is the El Guanaco gold mine, located near Guanaco in the Antofagasta Province, Chile.

Rarity

Extremely rare

For collectors

## Quality Criteria For such a rare micromineral, the primary criterion for value is the certainty of identification and the richness of the specimen – meaning the quantity and size of erazoite grains on the rock matrix. Samples with clearly visible aggregates and a rich association of other rare minerals are highly prized. ## Popular Localities All known collector specimens come from a single location – the El Guanaco mine in Chile. This is the only source of this mineral.

Care and storage

## Cleaning Erazoite specimens, being microscopic and delicate, should not be wet cleaned. For dust removal, use only a soft brush or carefully applied compressed air. ## What to Avoid Contact with water and all chemical agents, which can lead to oxidation and decomposition of sulfides, must be strictly avoided. The mineral is potentially sensitive to moisture and temperature changes. Ultrasonic cleaners must not be used. ## Storage It is recommended to store specimens in a dry, stable environment, preferably in a tightly sealed "perky box" to protect them from dust and moisture. Prolonged exposure to humid air can be harmful.

Sources

Read more