Mineral Resources, Economics and the Environment

Precious metals and gems were among the first minerals to be valued by civilization and they have kept their attraction for millennia. Even in their raw state, gems and precious metals are easily recognizable as truly special and beautiful. Although other minerals, such as pyrite (fool's gold), might be confused for gold, it is rare to confuse gold for another mineral. Its rich color and luster are simply unique. The same is true for the brilliant play of light and color from gemstones. On top of it all, precious metals and gems are rare. We even use special nomenclature to discuss their abundances. Gold and silver abundances are commonly reported in terms of the troy ounce, which equals about 31 g; prices of precious metals are commonly quoted in troy ounces, and we have used them (referred to here as ounces) to describe the metal endowment of individual deposits. Weights of diamonds and other precious gems are measured in an even smaller unit, the carat, which amounts to 0.2 g. Because these non-metric units are widely understood, we use them in parts of this discussion.

In spite of their rarity, precious metals and gems are a big business, with world production worth almost $200 billion (Figure 11.1). Gold is the most important of the group, with silver, diamonds, platinum-group elements (PGEs), and the colored gems emerald, ruby, and sapphire following in that order. Gold production increased in the 1990s, but has declined annually since 2000 in all countries except China. Global production of PGEs increased by more than 1,000% from 1960 to 2008, and plateaued thereafter. Production of gem diamonds increased by almost 1,400% at the start of the twenty-first century, dropped slightly during the economic crisis of 2008–2010, and leveled off after that. Mine production of industrial diamonds, which are discussed further in Chapter 13, increased from 1960 to 2008, although with cyclicity, but fell dramatically after 2008 owing to the proliferation of synthetic diamonds for industrial applications.