Surface Mining
Whenever the amount of overburden is such that a mineral deposit is economical to mine, surface-mining techniques are almost invariably chosen over underground mining, because surface mining has lower operational costs and fewer occupational hazards. There are two basic types of surface-mining operations: open-pit and strip mines. As shown in Figure 12.18, an open-pit mine nor-
FIGURE 12.18 Open-pit mines (A) typically involve irregularly shaped, low-grade deposits where large volumes of ore are removed. Terracing allows greater depths to be achieved and minimizes mass-wasting hazards. The Bingham Canyon copper mine (B) in Utah is the world’s largest excavation. The inset showing railroad cars on a single terrace step provides a sense of scale.