Fundamentals of Geology Practice Exam

Galena is a primary source of lead, which makes it the correct choice for this question. It is a lead sulfide mineral (PbS) and is the most important ore of lead, often forming in hydrothermal veins and as a replacement mineral in sedimentary rocks. Galena is characterized by its metallic luster and high density, and it commonly occurs in cubic crystals.

In the context of geology and mineral resources, the significance of galena extends beyond its lead content. It can also contain silver, which adds economic value. The extraction of lead from galena involves processes such as roasting and smelting, which separate lead from sulfur and other impurities.

The other minerals listed have their own economic significance but do not serve as major sources of lead. For instance, sphalerite is primarily an ore of zinc, hematite is mainly an iron ore, while chalcopyrite is primarily an copper source. Each of these minerals has distinct chemical compositions and industrial uses, but they do not contain lead in significant amounts as found in galena.