Types of Rocks and Minerals: What are we standing on?
Minerals are naturally formed, inorganic solid that has a definite crystalline structure. There are two types of minerals: silicate and nonsilicate. Silicate minerals are minerals that contain a combination of silicon and oxygen. Nonsilicate minerals are minerals that do not contain a combination of silicon and oxygen. A mineral can be identified using these seven things: color, luster, streak, cleavage and fracture, hardness, density, and special properties (if any). Color is telling what color the mineral is. Luster is telling the way the minerals surface reflects light. Streak is the color of the powdered form of the mineral. Cleavage and fracture is telling how a mineral breaks along a flat surface (cleavage) and along curved or irregular surfaces (fracture). Hardness it a mineral's resistance to being scratched. Density is the measure of how much matter is in a given amout of space. Special properties are properties that are particular to only a few types of minerals. For example, both magnetite and pyrrhotite are natural magnets that attract iron.
Rocks are classified into three categories: igneous, sedimentary, and metamorphic. These classes can be divided even further. Scientists know how to classify rocks by using the composition of the rock and the texture of the rock. The minerals of a rock determines the composition of that rock. For example, a rock made up of almost entirely quartz will have the same composition as the mineral quartz. The size, shape, and positions of the grains that make up a rock determine a rock's texture. The texture of a rock can provide clues as to how and where the rock formed. For example, depending on where the igneous rock formed, it can have either a fine-grained or a coarse-grained texture.
-Holt Science and Technology: Earth Science p.95-96; Picture: www.kgs.ku.edu
Rocks are classified into three categories: igneous, sedimentary, and metamorphic. These classes can be divided even further. Scientists know how to classify rocks by using the composition of the rock and the texture of the rock. The minerals of a rock determines the composition of that rock. For example, a rock made up of almost entirely quartz will have the same composition as the mineral quartz. The size, shape, and positions of the grains that make up a rock determine a rock's texture. The texture of a rock can provide clues as to how and where the rock formed. For example, depending on where the igneous rock formed, it can have either a fine-grained or a coarse-grained texture.
-Holt Science and Technology: Earth Science p.95-96; Picture: www.kgs.ku.edu