Formula: NiAs2
Arsenide, löllingite group,
low temperature orthorhombic
paramorph of isometric krutovite
and high temperature orthorhombic rammelsbergite
Crystal System: Orthorhombic
Specific gravity: 7.12 measured, 7.24 calculated
Hardness: 5½
Streak: Greyish black
Colour: Tin-white
Common impurities: Co,Cu,S
Environments
Pararammelsbergite occurs in hydrothermal veins bearing
nickel-cobalt sulphide mineralisation.
Associated minerals include nickeline,
skutterudite, cobaltite,
löllingite, gersdorffite and
rammelsbergite
(HOM).
Localities
There are three co-type Localities, the Hudson Bay mine, Coleman Township, Cobalt area, the Moose Horn mine, James
Township, Elk Lake area, and the Keeley-Frontier mine, South Lorrain Township, all in the Cobalt-Gowganda region,
Timiskaming District, Ontario, Canada.
At the Hudson Bay mine, one specimen consists almost entirely of pararammelsbergite. The associated minerals are
skutterudite, cobaltite and
gersdorffite (?) which tend to form rims outlining the margin of the main
mass of pararammelsbergite. In a section from another specimen, the cubic minerals, together with
löllingite, constitute about one-half of the surface. Typical
pararammelsbergite occupies the centres of spheroidal areas which are separated by the cubic minerals and
löllingite
(AM 25.561-577).
At the Moose Horn mine, a specimen section consists almost whoily of pararammelsbergite, associated with
interstitial nickeline and
skutterudite
in isolated grains and seams.
(AM 25.561-577).
At the Keeley mine, in a specimen with a reniform structure, the central part consists of pararammelsbergite
while the rim is made up of skutterudite and
gersdorffite (?)
(AM 25.561-577).
Alteration
Pararammelsbergite is the lower temperature paramorph of
rammelsbergite with an inversion temperature of 590oC in
equilibrium with nickeline. This inversion temperature is appreciably lowered
by inclusion of small quantities of cobalt and
sulphur in the lattice
(CM 9.128-131).
Back to Minerals