Skarn Deposits

Other types of deposits are closely related to intrusions. skarns are formed at the contact between a carbonate rock or a clastic sediment which is rich in carbonate and an intrusive rock. these are areas with irregular shape and have a characteristic composition in minerals, which are, iron silicates, magnesium and calcium. skarns are apt to contain zinc, gold or iron, but skarns are particularly important as hosts of tin ores, tungsten, molybdenum or copper. most of the time they occur on the margins of the intrusions that create deposits of porphyry copper.

Graite Hosted Deposits
Deposits of uranium, molybdenum, tungsten or tin very frequently occur inside and around granites, either in very coarse granite dykes called pegmatites or in veins. these coarse grained, granitic bodies are a source of many minerals which are rare, may of them can be cut into gems. Pegmatites are very commonly found as dykes in a large mass of plutonic rock of a finer size of grain. these deposits can also be useful sources of gemstones or fluorite. the deposits of tin in southwestern United Kingdom are a good example of these deposits.

Minable quantities of sapphires, rubies and emeralds have also been found in crystalline limestones, syenites, mica schists and other rocks besides pegmatites.