Placer Deposits

What is very possibly the simplest of the syngenetic deposits is the placer. If a mineral is stable chemically and is resistant physically, it can be eroded from its primary hard-rock occurrence and transported to river channels, deltas or other sedimentary environments where it can be deposited in a sedimentary bed. Diamonds, gold and other gemstones can be found in placer deposits due to the fact that they can withstand almost all geological underground and surface processes, they remain intact after the vast majority of other mineral constituents of a rock have been oxidized or altered.

The deposit can remain unconsolidated or it can aslo be buried and finally turned into a sedimentary rock. The conglomerates which bear the gold of South Africa and the conglomerates that bear uranium of Ontario are expandedly thought to be old gravel placers that have been solidified into rock formations.

The placer diamonds have been found in Venezuela, Brazil, India, the Democratic Republic of Congo and quite a few other African countries. During the past few years, the search for placer diamond deposits has also been extended to the floor of the ocean, notably off the southwestern coast of Africa. But just as all placer gold has its origins in bedrock of either one type or another; placers of gem minerals count some specific types of bedrock as a source.