Formula: PdHg
Alloy of palladium and mercury
Crystal System: Tetragonal
Specific gravity: 14.88 measured, 15.09 calculated
Hardness: 3½
Streak: Silver-white
Colour: Silver-white
Luminescence: Not fluorescent under UV
Solubility: Soluble in nitric acid (AM 13.491)
Common impurities: Cu

Plutonic igneous environments
Placer deposits

Potarite occurs in chromitite and dunite ultramafics, and in placers for gold and diamonds. Associated minerals include platinum, palladium, gold, palladium-mercury compounds, pentlandite, chalcopyrite, pyrrhotite and millerite (HOM).


At the Córrego Bom Sucesso placers, Serro, Minas Gerais, Brazil, platinumpalladium nuggets up to 1 mm in size have a botryoidal habit. A typical composite arborescent nugget comprises a broad irregular core region of massive gold-bearing potarite, or cavity space with relict potarite enclosed by a narrow zone of platiniferous palladium. Other nuggets comprise an arborescent to dendritic core of gold-bearing potarite, a broad internal zone of either pure platinum or palladian platinum and a narrow rim of platinum.
It is suggested that the Bom Sucesso nuggets resulted from high-level episodic hydrothermal alteration of mafic and ultramafic rocks within the drainage basin, with the remobilised platinum and palladium precipitated in open spaces in the enclosing metaquartzites (CM 40.341-355).

At the type locality, the Kaietur Falls, Potaro River, Kangaruma District, Potaro-Siparuni Region, Guyana, potarite occurs as placers of white metallic nuggets, usually very rounded due to the mineral's low hardness. Associated minerals include diamond, palladium and platinum (Mindat).

At Inatsumiyama, Nichinan, Hino District, Tottori Prefecture, Japan, palladium-rich platinum-group minerals have been found in sulphide-bearing dunites and harzburgites from the ultramafic complex. In the dunite, potarite is the most abundant platinum-group mineral but other associated platinum-group minerals include stibiopalladinite and rare sperrylite, and palladium-rich alloys. A palladium telluride has been found in the harzburgites. The platinum-group minerals are usually enclosed by pentlandite-heazlewoodite composite grains and, rarely, by altered chromium-rich spinel. These minerals are characteristic of an ultramafic assemblage but here they are accompanied by ubiquitous galena and minor sphalerite, that are not usually associated with such assemblages. The ultramafic part of this complex has been thermally metamorphosed (olivine-talc zone) within the contact aureole of an adjacent granite. The platinum-group minerals, sulphides and altered spinel are all intergrown with antigorite and/or chlorite, indicating a metamorphic overprint on the primary igneous mineralogy. It is possible that potarite and the other platinum-group minerals formed at temperatures of up to 650oC (MM 63.369-377).

Back to Minerals