Skarn is a Swedish term which Swedish miners use for
calling coarse-crystal calcium silicate mixture which
are found in association with iron ore deposits in the
Sweden’s iron mines. At the early stages of previous
century, this term enters scientific definitions of
Based on scientific definition, when a hot magmatic
intrusive massive enters a complex of sedimentary
rocks, such as limestone, dolomite or calcareous
shale, first surrounding rocks of intrusive massive
are metamorphosed up to tens of meters. This
metamorphism includes calcite crystal growth and
conversion of limestone to marble. This metamorphosed
region is called metamorphic halo. For skarns, the
process does not end to this point. Mineral-making
solutions originating from magma move towards
carbonate metamorphic halo and react with it. This
phenomenon appears in high temperature and pressure
surrounding igneous massives becoming cool. The
mentioned reactions produce two groups of new minerals
in the metamorphic halo. Group 1 includes calcium
silicate minerals, like calcium-bearing garnets,
epidote, actinolite, hedenbergite, zoisite, etc. This
group of minerals is called calc-silicates. The origin
of their calcium is from carbonate sedimentary rocks
(limestone and dolomite), and elements, such as Fe,
Mg, Si, Na and Al originate from magmatic solutions.
Group 2 includes oxide and sulfide-bearing minerals
crystallizing directly from magmatic solutions and
form main mineral in ore deposit. These minerals are;
pyrite, chalcopyrite, bornite, magnetite and hematite.
Their composition severely depends on magmatic
solution compounds. The most important properties of
skarns are as follows; relatively-big crystals and
copper, iron and calc-silicates are in form of a
mixture. Skarns are the most important source of
tungsten in the world. The most important minerals
which are exploited from skarns are as follows;
Copper, iron, molybdenum, lead, zinc and also
important industrial minerals, such as garnet,
wollastonite, asbestos, flogopite and talc.
Skarn ore deposits are formed during different
geological times from Precambrian to Cenozoic.
Besides iron, these skarns, include cobalt and nickel.
These reserves may develop from hundreds of meters to
several kilometers. They are located between
intrusive massifs and surrounding carbonate rocks.
The composition of intrusive massif varies between
gabbro-diorite to quartz-monzonite. Carbonate rocks
are in simple form or dolomite. Calc-silicate
minerals of these skarns are; garnet (andradite and
grossular), pyroxene (hedenbergite and diopside),
epidote (quartz), calcite, chlorite. Main minerals
have magnetite and hardly hematite. The reserve of
these ore deposits is usually between 5 to 1000
million ton and its iron carat is 33 to 55%. Mines of
iron-bearing skarns are found in the former Soviet
Union, Cuba, the Philippines and Japan.
Copper skarns are found near calc-alkaline intrusive
massives bearing granodiorite to monzonite composition
bearing carbonate rocks. These skarns often belong to
Mesozoic and Paleozoic. Calc-silicate minerals are;
garnet, andradite, diopside, serpenthine and main
non-silicates are chalcopyrite, pyrite and less amount
of molybdenite. Molybdenum can be obtained from
Copper carat of these ore deposits varies between 5.3
to 8%, and their reserve varies between 75 to 135
million ton of copper ore.
