There are two ways to remove coal from the ground: surface mining and underground mining. Surface mining is used when a coal seam is relatively close to the surface, usually within 200 feet. The first step in surface mining is to remove and store the soil and rock covering the coal (called the overburden).
Pearl oysters are not closely related to true oysters, being members of a distinct family, the feathered oysters (Pteriidae). Both cultured pearls and natural pearls can be extracted from pearl oysters, though other molluscs, such as the freshwater mussels, also yield pearls of commercial value.
A favorite among exotic foods, oysters are a naturally rich source of zincâan essential element of the collagen-building process. Also chock-full of vitamins and minerals including iron and vitamin B12, oysters provide a low-calorie option and a long list of health benefits.