Hexamolybdenum

Chemical formula: (Mo,Ru,Fe,Ir,Os)

Hexamolybdenum is an extremely rare, naturally occurring alloy of platinum group metals, mainly molybdenum and ruthenium, found as microscopic grains.

## Characteristics Hexamolybdenum is a mineral from the native elements group, specifically a natural metal alloy. Its composition primarily includes molybdenum and ruthenium, with minor admixtures of iron, iridium, and osmium. It occurs as extremely small, rounded or irregular grains, usually not exceeding a few tens of micrometers in size. Due to its microscopic size, its visual features are difficult to observe without specialized equipment. In reflected light under a microscope, it has a creamy white color with a pinkish hue. ## Physical Properties This mineral is opaque and characterized by a metallic luster. Its hardness and density have not been precisely measured due to the small size of the grains, but they are estimated to be high, typical for metal alloys. It is isotropic. ## History and Name The name "heksamolibden" (heksamolybdenum) refers to its hexagonal crystallographic system and the dominant molybdenum in its composition. The mineral was first described in 1995 by J. Jedwab, M. Cassard, and J.P. Milesi based on material from river sediments in the Apurímac region of Peru.

Properties

Luster
Metallic
Cleavage
None
Fracture
Hackly
Transparency
Opaque
Crystal system
Hexagonal

Diagnostic features

## Identification Identification of hexamolybdenum is possible only with advanced laboratory techniques, such as reflected light ore microscopy and chemical composition analysis using an electron microprobe (EDS/WDS). Its characteristic features include a creamy white color with a pinkish hue in reflected light and a specific chemical composition dominated by molybdenum and ruthenium. ## Distinguishing from similar minerals It can be confused with other natural platinum group metal alloys, such as osmiridium or rutheniridosmine, as well as native osmium, iridium, or platinum. Definitive differentiation requires quantitative chemical analysis. ## Crystal forms This mineral forms crystals with hexagonal symmetry. It occurs as very small, rounded or irregular grains, often as inclusions in other minerals.

Geological environment

## Genesis Hexamolybdenum is a mineral of magmatic origin. It crystallizes in ultramafic igneous rocks, such as dunites and chromitites, associated with ophiolite complexes. As a result of erosional and weathering processes of these rocks, chemically and physically resistant hexamolybdenum grains can be released and concentrated in secondary deposits, such as alluvial river sediments (so-called placer deposits). ## Mineral associations It coexists with other platinum group minerals (PGM), such as laurite, irarsite, osmiridium, as well as chromite, magnetite, and serpentine group minerals. ## Locations The most important confirmed occurrences of this mineral are the discovery site in river sediments in the Apurímac region of Peru and occurrences in chromitites of the Sagua de Tánamo ophiolite in Cuba. It has also been reported in the Freetown igneous complex in Sierra Leone.

Rarity

Extremely rare

For collectors

## Quality criteria As a mineral of microscopic size, hexamolybdenum is not acquired for aesthetic purposes. The scientific and collector value of a specimen lies in the confirmed presence of this rare mineral in the host rock (most often in chromitite) or in a heavy mineral concentrate. The most valuable specimens are those from the type locality (Peru) and those that have been analyzed and thoroughly documented.

Care and storage

## Cleaning Due to its microscopic size and occurrence as inclusions or fine grains in sediments, individual specimens of hexamolybdenum are not subject to cleaning under collector conditions. ## What to avoid Specimens (most often in the form of polished sections) should be protected from aggressive chemicals and mechanical damage that could scratch the surface and destroy the microscopic mineral grains. ## Storage Storage primarily concerns the host rock or polished sections containing hexamolybdenum. They should be kept under stable conditions, in boxes protecting them from dust and mechanical damage.

External references

Sources

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