About 80 percent of the world's tin deposits occur
not as primary lodes, but as unconsolidated
secondary or placer deposits in river beds and
valleys or on the sea floor. The largest concentration
of both onshore and offshore placers is in the
extensive tin belt of South-East Asia, which
stretches from China in the north, through Thailand,
Burma and Malaysia, to the islands of Indonesia in
the south.
Compared with commercially viable deposits of
copper, lead, zinc, nickel and bauxite, tin deposits
are generally small. Further, tin is almost always
found closely allied to the granite from which it
originates.