Jacutingaite

Chemical formula: Pt₂HgSe₃

Jacutingaite is a rare platinum-mercury selenide, forming tiny, hexagonal lamellae with a metallic luster, found in gold and palladium deposits.

## Characteristics Jacutingaite is a very rare mineral from the selenide group, chemically classified as a platinum-mercury selenide. It occurs as very small, hexagonal, platy crystals, rarely exceeding a few tens of micrometers in size. It typically forms inclusions within other minerals. It is opaque and has a metallic luster and a gray color. ## Physical Properties This mineral is characterized by a hardness of 3.5 on the Mohs scale. It possesses perfect cleavage in one direction, corresponding to its platy structure. Its streak is gray. ## History and Name The mineral's name comes from the term "jacutinga," a local Brazilian name for gold- and palladium-rich hematitic clays where it was first found. It was described as a new mineral species in 2011 by Andrew C. Roberts and his research team, and approved by the International Mineralogical Association (IMA) under number 2010-035. The type locality is the Cauê mine in Itabira, Minas Gerais state, Brazil. ## Uses Due to its extreme rarity and microscopic size, jacutingaite has no industrial applications. It is solely an object of scientific interest and a collector's item for specialized micromineral collectors.

Properties

Mohs hardness
3.5
Luster
Metallic
Streak
gray
Cleavage
{001}
Transparency
Opaque
Crystal system
Trigonal

Diagnostic features

## Identification Identification of jacutingaite is possible only through advanced laboratory methods, such as chemical composition analysis (EDS/WDS) using an electron microscope and X-ray diffraction (XRD). Visually, under high magnification, tiny, hexagonal lamellae with a metallic luster can be observed. ## Distinguishing from similar minerals Due to its microscopic size, distinguishing it from other rare platinum-group minerals, selenides, or sulfides (e.g., potosíite, sudovikovite) is impossible without specialized chemical analysis. Its unique composition (combination of Pt, Hg, and Se) is a key diagnostic feature. ## Crystal forms Jacutingaite forms thin, hexagonal lamellae and plates. It occurs as single, dispersed crystals or small aggregate inclusions within other minerals.

Geological environment

## Genesis Jacutingaite forms under specific hydrothermal conditions, in mineralization zones rich in platinum-group elements (PGEs), gold, and selenium. Its crystallization is associated with processes occurring in gold and palladium deposits hosted in hematitic rocks. ## Mineral associations This mineral co-occurs with other rare minerals, such as native gold, native palladium, native platinum, as well as with platinum-group minerals, hematite, potosíite, atheneite, and sudovikovite. ## Localities The only confirmed and described occurrence of jacutingaite in the world is its type locality – the Cauê mine in Itabira, Minas Gerais state, Brazil. This is one of the world's most important iron deposits, also known for the occurrence of rare gold and platinum-group minerals.

Rarity

Extremely rare

For collectors

## Quality criteria For such a rare micromineral as jacutingaite, the most important criterion is the confirmed presence of the mineral on the specimen itself. Additional value is given to specimens where the crystals, despite their microscopic size, are well-formed, have a distinct hexagonal outline, and are undamaged. Association with other rare minerals, such as native gold, is also significant. ## Popular localities The only source of specimens is the Cauê mine in Brazil. Finding jacutingaite outside this locality would be a discovery of global significance.

Care and storage

## Cleaning Specimens containing jacutingaite, typically microminerals, do not require cleaning. Any attempt at mechanical or chemical cleaning can irrevocably damage the delicate crystals. If dust removal is necessary, use compressed air from a safe distance. ## What to avoid Avoid contact with chemicals, acids, and ultrasonic cleaners. The mineral is soft and brittle, so it should be protected from scratches and impacts. ## Storage Specimens should be stored in specialized micromount boxes to protect them from mechanical damage and dust. Avoid extreme temperatures and humidity.

External references

Sources

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