Chapter 2 : Minerals Discussion Chapters 2 and 3 discuss minerals and rocks, the materials that make up the solid Earth, or geosphere. We discuss the nature of minerals and rocks, the processes by which they form and change, and the many ways in which they effect humans and our environment. We open Chapter 2 with a description of vermiculite mining in northwestern Montana, to stress that minerals are an important aspect of our environment, but that environmental problems arise when we extract them. We return to the environmental aspects of minerals throughout the chapter. We continue the discussion of minerals by pointing out that all rocks are made of one or more minerals. Therefore, minerals are the fundamental building blocks of the Earth. For this reason, an appreciation of the nature of minerals and a basic knowledge of the few, common, rock-forming minerals lays a foundation for the study of the Earth. We describe two aspects of minerals that commonly fascinate introductory geology students because they are familiar: crystals and gems. Class interest can be stimulated by pointing out that the striking crystal faces of diamonds and other gems results from the perfect ordering of atoms in the crystals, and that many gems are simply beautiful varieties of common minerals. The knowledge that only a few minerals are common, and that they can be identified correctly with a bit of practice, is another aspect of the study of minerals that draws most students into the subject. It seems to give students a good feeling to know that only a few minerals are abundant, and therefore they can easily learn to identify most minerals in most rocks. The chapter explains that the essential nature of a mineral is that it has a crystalline structure -- an orderly, repetitive, arrangement of atoms -- and a definite chemical composition. We then describe the physical properties of minerals and explain how these properties can be used to identify minerals. We stress the point, however, that the most important aspect of field identification is recognition of common minerals, aided by a few simple tests of physical properties.
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