Sulfate minerals are a group of
about 200 minerals.
They tend to be soft,
low in densities and light in colour.
The most common
minerals in the group are gypsum and barite.
Others include anglesite, anhydrite, glauberite, epsomite, brochantite
Barite crystals. By Ed Uthman via Flickr.com
the most common
sulfate mineral. It forms tabular or prismatic crystals or crested
aggregates. Other possible habits are fibrous, stalactitic and massive.
It is a soft and relatively heavy mineral to be a sulfate. It is found
in hydrothermal veins associated with calcite, fluorite, sphalerite and
is the second most common sulfate mineral. It is a calcium sulfate
hydroxide and it is an evaporative mineral. It can form large, very
spectacular, tabular or prismatic crystals, or be fibrous, granular or
massive. It can be colourless, white, reddish, brownish, yellowish,
greenish or grey. It forms in evaporative deposits.
Anglesite. By Gary Parent via Flickr.com
a less common
mineral, which can form pyramidal, prismatic or tabular crystals, or be
compact, granular or massive. It can be white, colourless, blueish,
greenish, yellowish or grey. It is a lead sulfate, and forms in
oxidation zones of lead deposits. It can be found associated to galena.
Anhydrite. By Ron Schott via Flickr.com
a calcium sulfate,
which is a waterless form of gypsum. It can form prismatic or tabular
crystals, or be granular or massive. It can be white, colourless, grey,
reddish or brownish. In humid condition it alters to gypsum. It is
found in evaporative deposits associated to halite and gypsum.
Glauberite. By Alisha Vargas via Flickr.com
is a sodium
calcium sulfate, which can form tabular or prismatic crystals. It is
most often yellowish or grey, but can also be reddish or colourless. It
forms most commonly in evaporative deposits where areas of salt lakes
or marine lagoons dry out, but can also be found in mafic igenous rocks
and volcanic fumaroles.
Epsomite. By Genista via Flickr.com
sulfate, which rarely forms crystals but most often is stalactitic,
massive or occurs as acicular crusts. It can be white, colourless,
greenish or pinkish. It is an important source of magnesuim salts and
it forms in limestone caves, rock faces in mines, and in oxidised zones
of pyrite deposits.
Brochantite. By MuseumWales via Flickr.com
is a copper sulfate
hydroxide. It forms tabular, acicular or prismatic crystals but can
also be found in fine grained masses or druse crusts. It can
different shades of green in colour. It forms in oxidised zones of
copper deposits and can be associated to malachite, azurite and other
Celestite crystal. By meganpru via Flickr.com
is a strontium sulfate, which forms tabular or prismatic crystals, or
be nodular, granular, fibrous or massive. It can be white, colourless,
blue, brown, green or red in colour. It forms in evaporative deposits
as well as in sedimentary rocks such as sandstones,
and hydrothermal veins.