Placer deposit

[3] Valuable mineral components often occurring with black sands are monazite, rutile, zircon, chromite, wolframite, and cassiterite.

[1] A hardness greater than quartz is desired, however substances such as gold typically deform and create irregularly shaped nuggets when subject to mechanical stress.

[2] Typical locations for alluvial gold placer deposits are on the inside bends of rivers and creeks; in natural hollows; at the break of slope on a stream; the base of an escarpment, waterfall or other barrier.

Alluvial placers are formed by the deposition of dense particles at a site where water velocity remains below that required to transport them further.

To form a placer deposit, the particles desired must show a marked density contrast with the gangue material, which is able to be transported away from the trap site.

[citation needed] Gold bearing beach placers consist of large strips of black sands and are typically constantly changing as a result of storms or sporadic wave action.

[4] Aeolian placers are valuable minerals found in arid regions freed from their source rock by wind actions.

[6] Historically, aeolian placers have been mined by hand with simple tools by miners due to the proximity to the surface, and small concentration.

[4] Aeolian placers are common in Australia and the Western United states, where the climate is arid and the ground is relatively level leaving wind as the primary erosion force.