Placer deposits of native gold and platinum are concentrated largely on the basi
ID: 157845 • Letter: P
Question
Placer deposits of native gold and platinum are concentrated largely on the basis of:A. The late stage of cooling of igneous minerals in Bowens reaction series. B. The chemical weathering of these two metals. C. The specific gravity of these two metals. D. The specific gravity of the sulfide ore minerals containing these two metals. Placer deposits of native gold and platinum are concentrated largely on the basis of:
A. The late stage of cooling of igneous minerals in Bowens reaction series. B. The chemical weathering of these two metals. C. The specific gravity of these two metals. D. The specific gravity of the sulfide ore minerals containing these two metals.
A. The late stage of cooling of igneous minerals in Bowens reaction series. B. The chemical weathering of these two metals. C. The specific gravity of these two metals. D. The specific gravity of the sulfide ore minerals containing these two metals.
Explanation / Answer
C
Placer deposit, natural concentration of heavy minerals caused by the effect of gravity on moving particles. When heavy, stable minerals are freed from their matrix by weathering processes, they are slowly washed downslope into streams that quickly winnow the lighter matrix. Thus the heavy minerals become concentrated in stream, beach, and lag (residual) gravels and constitute workable ore deposits. Minerals that form placer deposits have high specific gravity, are chemically resistant to weathering, and are durable; such minerals include gold, platinum, cassiterite, magnetite, chromite, ilmenite, rutile, native copper, zircon, monazite, and various gemstones.