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Minerals Chapter 3 Sec. 1 & 2 What Is a Mineral? • A mineral is a naturally formed, inorganic solid that has a definite crystalline structure. • All minerals contain one or more of the 92 naturally occurring elements. What is a Mineral? • Answer four questions. • If any answer is “no” – NOT a mineral! What is a Mineral? • 1) Is it nonliving material? • 2) Is it a solid? • 3) Is it formed in nature? • 4) Does it have a crystalline structure? What Are Crystals? • Crystals are solid, geometric forms of minerals • Repeating pattern of atoms or molecules creates the crystals • A crystal’s shape is determined by the arrangement of the atoms or molecules within the crystal. Crystal Structures Two Groups of Minerals Silicate vs. Nonsilicate • Silicate Minerals: Minerals that contain a combination of silicon and oxygen molecules. These minerals make up more than 90% of Earth’s crust. Examples: Quartz, Feldspar, and Mica. • Nonsilicate Minerals: Minerals that do not contain a combination of the elements silicon and oxygen. They are made up of carbon, oxygen (without silicon), fluorine, and sulfur. Examples; Copper, Calcite, Fluorite, and Gypsum Identifying Minerals • There are seven ways to determine the identity of minerals. Color • Not usually the best way to identify a mineral; for reasons such as impurities. Luster • The way a surface reflects light; usually described as shiny or dull • Shiny = metallic luster • Dull = submetallic, nonmetallic • Observe samples Streak • The color of a mineral in powdered form. • A mineral’s streak can be found rubbing the mineral against a piece of unglazed porcelain called a streak plate. Cleavage and Fracture • Cleavage: the tendency of some minerals to break along smooth, flat surfaces. • Fracture: the tendency of some minerals to break unevenly along curved or irregular surfaces. This sample of quartz shows a curved fracture pattern called conchoidal fracture. Hardness • A mineral’s resistance to being scratched. • Scientists use Mohs hardness scale to determine the hardness of minerals. • ***The greater a mineral’s resistance to being scratched is, the higher the mineral’s rating is. Moh's Hardness Scale Density • The measure of how much matter is in a given amount of space. Special Properties • Some minerals can be identified by special properties they have, such as taste (NEVER taste in science class!), magnetism, fluorescence, radioactivity, chemical reaction, and optical properties. Special Properties What are Rocks? • Rocks are a combination of one or more minerals.