what is the definition of this deposit type you mentioned?
Placer deposit or placer is an accumulation of valuable minerals formed by gravity separation from a specific source rock during sedimentary processes.Placer mining is an important source of gold
Placer deposit
 a placer deposit or placer is an accumulation of valuable minerals formed by gravity separation from a specific source rock during sedimentary processes. The name is from the Spanish word "placer", meaning "alluvial sand". Placer mining is an important source of gold, 
what is coconut crab? It is a species of terrestrial hermit crab, also known as the robber crab or palm thief. It is the largest land-living arthropod in the world what are the classification of the above mentioned species of crab? Squat lobsters and porcelain crabs describe the former mentioned Squat lobsters are dorsoventrally flattened crustaceans with long tails held curled beneath the cephalothorax. how are these classified? Squat lobsters were placed together in the superfamily Galatheoidea alongside the porcelain crabs of the family Porcellanidae. what is the evolution of the just mentioned type of crab? They are an example of carcinisation, whereby a noncrab-like animal (in this case a relative of a squat lobster) evolves into an animal that resembles a true crab. what is its diversity? Some 4723 extant species porcelain crab had been described, divided among these 30 genera what is its ecological significance? Porcelain crabs live in all the world's oceans, except the Arctic Ocean and the Antarctic. what are the climate in this ocean? Polar climate characterized by persistent cold and relatively narrow annual temperature ranges. what is its geological significance? The crystalline basement rocks of mountains around the Arctic Ocean were recrystallized or formed during the Ellesmerian orogeny, the regional phase of the larger Caledonian orogeny in the Paleozoic, creating many of the reservoir for current day oil and gas deposits. what are the natural resources? Petroleum and natural gas fields, placer deposits, polymetallic nodules, sand and gravel aggregates.
wiki:13613602
Placer deposit [SEP] Introduction
In geology, a placer deposit or placer is an accumulation of valuable minerals formed by gravity separation from a specific source rock during sedimentary processes. The name is from the Spanish word "placer", meaning "alluvial sand". Placer mining is an important source of gold, and was the main technique used in the early years of many gold rushes, including the California Gold Rush. Types of placer deposits include alluvium, eluvium, beach placers, and paleoplacers. Placer materials must be both dense and resistant to weathering processes. To accumulate in placers, mineral particles must be significantly denser than quartz (whose specific gravity is 2.65), as quartz is usually the largest component of sand or gravel.