Menshikovite

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Formula: Pd₃Ni₂As₃
Arsenide, palladium- and nickel- bearing mineral
Crystal System: Hexagonal
Specific gravity: 10.65 calculated
Hardness: 5
Streak: Grey
Colour: White
Environments

Plutonic igneous environments

Localities

At the Vostok deposit, Lukkulaisvaara ultrabasic Massif, Olanga River, Oulanka plutonic complex, Loukhsky District, Republic of Karelia, Russia, menshikovite was discovered in a mineralised pod of coarse-grained, entirely altered gabbronorite, associated with a micro gabbronorite. The gabbronorite is strongly enriched in disseminated base-metal sulphides, dominantly chalcopyrite, pentlandite and violarite, which is a product of replacement of the primary pentlandite. This rock is rich in palladium, silver and platinum.
The main platinum group minerals at the Vostok deposit are merenskyite, kotulskite–sobolevskite and michenerite. These minerals commonly occur as intergrowths which also include hessite. Unusual and rare minerals that occur in the Vostok deposit include hollingworthite that contains a very high concentration of osmium, and a rhodium-bearing cobaltite–gersdorffite associated with this hollingworthite.
Menshikovite typically forms anhedral grains associated with chalcopyrite and pentlandite. Merenskyite rich in bismuth and kotulskite–sobolevskite, also bismuth-rich, may occur as tiny inclusions in, or as minute grains attached to, menshikovite (CM 40.2.679-692).

At the type locality, the Chineyskoye Fe-Ti-V deposit, Chiney massif, Zabaykalsky Krai, Russia, the complex consists of interlayered gabbro, gabbronorite, anorthosite and pyroxenite. In addition, layers of rocks enriched in titanium-bearing magnetite are present in the lower part of the complex. Zones of palladium-rich mineralisation are associated with base-metal sulphides at the lower contact of the Chiney intrusion with the quartz–feldspar sandstones.
Menshikovite was discovered in heavy-mineral concentrates, obtained from samples of the mineralised quartz–feldspar sandstones which are metasomatically altered, recrystallised or hornfelsed. The major minerals in the mineralised rocks are micas (mainly biotite and minor muscovite), amphibole and chlorite.
The ore minerals identified in the heavy-mineral concentrates in association with menshikovite are chalcopyrite, bornite, ilmenite, cobaltite–gersdorffite, palladium-rich maucherite, nickeline, sperrylite, isomertieite, majakite, mertieite or stibiopalladinite, michenerite, arsenic-rich paolovite, hollingworthite and a gold-silver alloy (CM 40.2.679-692).

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