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Minerals • Minerals come in many colors and shapes. Minerals can be as rare as a precious diamond. Or they can be as common as halite, which you know as table salt. Geologists have identified more than 3,000 different minerals. But all of these minerals share certain characteristics.
Minerals • A mineral is a solid, inorganic material that forms naturally on or beneath Earth’s surface. Almost all minerals have crystal structure. Each mineral also has a definite chemical composition.
Minerals--SOLID A mineral is a solid, inorganic material that forms naturally on or beneath Earth’s surface. Almost all minerals have crystal structure. Each mineral also has a definite chemical composition. • Solid—a material with a definite volume and definite shape. Minerals generally remain solid under ordinary conditions on Earth’s surface. But high temperatures inside Earth can cause minerals deep beneath the surface to melt.
Minerals--INORGANIC A mineral is a solid, inorganic material that forms naturally on or beneath Earth’s surface. Almost all minerals have crystal structure. Each mineral also has a definite chemical composition. • Inorganic—A material that is inorganic did not arise from a living thing. For instance, coal is not a mineral because it is formed from the remains of plants that lived millions of years ago.
Minerals—NATURALLY OCCURING A mineral is a solid, inorganic material that forms naturally on or beneath Earth’s surface. Almost all minerals have crystal structure. Each mineral also has a definite chemical composition. • Naturally Occurring—A substance that is naturally occurring is the result of processes that take place in the natural world. Materials made by people, such as cement, plastic, glass, and steel, are not minerals.
Minerals—CRYSTAL STRUCTURE A mineral is a solid, inorganic material that forms naturally on or beneath Earth’s surface. Almost all minerals have crystal structure. Each mineral also has a definite chemical composition. • Crystal Structure—The repeating pattern of a mineral's atoms forms a solid called a crystal. You can break a large piece of a crystal into smaller pieces. But the smaller pieces still have a cubic crystal structure.
Minerals—CHEMICAL COMPOSITION A mineral is a solid, inorganic material that forms naturally on or beneath Earth’s surface. Almost all minerals have crystal structure. Each mineral also has a definite chemical composition. • Definite Chemical Composition—Every mineral is made up of certain elements in definite proportions. For example, the mineral halite is made up of one atom of sodium for every atom of chlorine.
Identifying Minerals • Some properties of minerals include: • Hardness • Color • Streak • Luster • How a mineral breaks apart • Density
Mohs Hardness Scale • Geologists use a scratch test to determine the hardness of minerals on the Mohs scale. The scratch test compares the hardness of a mineral sample with minerals on the scale.
Mohs Hardness Scale • If you tested the harness of a piece of halite, you would find that halite can scratch gypsum. Halite, however, cannot scratch calcite. Therefore, halite’s hardness is between the hardness of gypsum and calcite, or between 2 and 3 on Mohs scale.