|
.
Covellite
Mineral Facts:
Chemical
Formula:
CuS
Covellite, or
indigo copper, is the cupric sulfide,
chalcocite being
the corresponding cuprous salt. It is called indigo copper because of
the deep blue color of its fresh fracture.
It usually contains a
little iron and often traces of lead and silver.
Colors:
Deep indigo blue,
frequently iridescent.
The streak is
lead-gray to black.
Hardness:
1.5 to 2
Density:
4.59
Cleavage:
The mineral has
one perfect cleavage parallel to the basal plane.
In thin splinters it
is flexible.
Crystallography: Orthorhombic
Covellite
usually occurs
in massive forms.
Crystals of covellite are not
common,
but
it does occur rarely in
tabular hexagonal crystals with prominent basal plane.
Luster:.
Metallic luster.
|
Covellite Copper ore (blue) |
|
Composition, Structure and
Associated Minerals:
Covellite is a
rare mineral, found only in the enriched sulfide zone of copper deposits,
associated with chalcocite,
bornite, etc.
Is formed in
the zone of secondary enrichment in copper veins. This zone is situated
between the leached and oxidized gossan and the unaltered zone near the
water table. It forms as the product of the chemical action between the
original vein stuff and descending leached solutions, and by the combination
of both, it often forms the richest
copper ore found in the lode.
It is a good electrical
conductor.
Identification
and Diagnostics
Before the
blowpipe,
covellite
is fusible at 2.5. The
reactions of covellite are like those of chalcocite, with these exceptions:
Covellite burns with a blue flame when heated on charcoal giving off an odor
of sulfur dioxide. It yields a sublimate of elemental
sulfur in the closed
tube. The roasted mineral, when moistened with hydrochloric acid and
ignited, gives a green flame (positive test for copper). When moistened with
water shows a strong purple color. Covellite is distinguished from other
minerals than chalcocite by its reactions for Cu and S and the absence of
reactions for Fe. It is distinguished from chalcocite by its color and
density and by the fact that it ignites on charcoal.
Localities
Covellite (CuS)
is a copper sulfide, CuS, occurring massive usually, and indigo blue in
color. While
the mineral is comparatively rare, it is abundant in Chile and Bolivia and
at Butte, Montana. It is also found in crystals on the lava of Vesuvius and
elsewhere. It usually occurs as an alteration product of other copper-sulfur
compounds, especially in the zone of secondary enrichment of copper veins.
Uses. It is mined with other copper minerals and is used as a source of
copper.
Covellite is
found in Chile, Mansfeld, Germany, etc. It is often mixed with other copper
compounds from which it has been derived by alteration. It is an minor
ore of copper that is locally important in some mines.
.Return
to the
Mineral Collectors Information Page |
|
