Jolliffeite

Chemical formula: Ni<sup>3+</sup>(AsSe)<sup>3-</sup>

Jolliffeite is an extremely rare nickel arsenide and selenide, forming microscopic, metallic grains in uranium deposits.

## Characteristics Jolliffeite is a nickel arsenide and selenide, occurring as extremely small, metallic grains, usually not exceeding 100 micrometers in size. When observed under a reflected light microscope, it is gray to grayish-white with a slight pinkish tint. It is an opaque mineral with a metallic luster. ## History and Name The mineral was named in honor of Alfred "Fred" Walton Jolliffe (1907–1988), a Canadian geologist who made significant contributions to the understanding of the geology of northern Canada, including the Great Slave Lake region, where the mineral was discovered. It was approved by the IMA in 1991. ## Uses Due to its extreme rarity and microscopic size, jolliffeite has no commercial or industrial applications. Its significance is purely scientific and mineralogical.

Properties

Mohs hardness
5.5
Luster
Metallic
Streak
Black
Density
7.45
Cleavage
None
Fracture
Uneven
Transparency
Opaque
Crystal system
Cubic

Diagnostic features

## Identification Identification of jolliffeite is only possible using advanced laboratory techniques, such as reflected light microscopy, electron microprobe (EDS/WDS), and X-ray diffraction (XRD). In reflected light, it exhibits a characteristic grayish-white color with a pinkish tint and is isotropic. ## Distinguishing from Similar Minerals It can be confused with other metallic ore minerals occurring in the same parageneses, such as gersdorffite, nickeline, or clausthalite. Definitive differentiation requires chemical analysis to confirm the simultaneous presence of nickel, arsenic, and selenium in appropriate proportions. ## Crystal Forms Jolliffeite forms anhedral (irregular), rounded grains, typically 5 to 100 micrometers in size. It sometimes occurs as rims around other minerals, e.g., uraninite.

Geological environment

## Genesis Jolliffeite is a hydrothermal mineral. It forms under low-temperature conditions in carbonate-hematite veins cutting uranium deposits. It occurs in paragenesis associated with uranium mineralization processes. ## Mineral Associations This mineral co-occurs with uraninite, clausthalite, hematite, quartz, dolomite, anilite, digenite, covellite, bornite, chalcopyrite, pyrite, gersdorffite, and nickeline. ## Localities The only confirmed locality of jolliffeite worldwide (type locality) is the Fish Hook Bay uranium deposit, located on the Shirley Peninsula on Lake Athabasca in Saskatchewan, Canada.

Rarity

Extremely rare

For collectors

## Quality Criteria As a microscopic mineral, jolliffeite is not traded on the collector's market as isolated specimens. Its value is purely scientific. Rock fragments from the type locality, containing analytically confirmed jolliffeite grains, may be potentially valuable for specialized research institutions. The value of such material depends on the richness of the mineral association and the quality of scientific documentation.

Care and storage

## Cleaning Due to its microscopic nature and occurrence as inclusions within other minerals, specimens containing jolliffeite do not require and should not be subjected to cleaning. ## What to Avoid Avoid all chemical and mechanical treatments that could damage the delicate surface of the host rock and destroy the microscopic mineral grains. As a mineral containing arsenic and selenium, avoid inhaling dust and wash hands after contact with the specimen. ## Storage Specimens should be stored under stable conditions, in closed collector boxes, to prevent dust accumulation and accidental damage. Protect them from moisture and extreme temperatures.

External references

Sources

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