Outline+HomeWork

**Mineral Characteristics**
-Earths crust is composed of 3000 minerals -A mineral is a naturally occurring inorganic solid with specific chemical composition and a definite crystalline structure

**Crystal**
-atoms are arranged in geometric patters that are repeated - a solid in which the atoms are arranged in repeating patterns

Variations in Composition
-chemical composition can vary slightly -Both calcium and sodium are incorporated in the crystalline structure

**Rock-forming minerals**
-30 out of 3000 minerals are common -make up most of the rocks in earth's crust -molten materials=magma -when magma cools it crystalizes to form minerals -rate of cooling determines crystal size (slower=larger) -minerals often dissolved in water

**Identifying Minerals**
identify using: -crystal form-shape -luster-reflects light (metallic and nonmetallic) -hardness-how easily it can be scratched -cleavage & fracture-atomic arrangement and how it breaks -streak-the powder color a mineral leaves when rubbed across an unglazed porcelain plate -color-color of mineral -texture-feel of the mineral -density & specific gravity-D=M/V (how compact the mineral is) -German geologist Friedrich Mohs developed a scale by which an unknown mineral's hardness can be compared to the known hardness of ten minerals. -Talc is one of the softest minerals, represents 1 on Mohs scale of mineral hardness. -Diamond is so hard it represents 10 on the Mohs scale of mineral hardness. ****Mineral Groups**** -Thousands of different minerals -Silicates-minerals that contain silicon and oxygen -Oxides-compounds of oxygen and a metal

**Economic Minerals**
-Ores-contains a valuable substance that can be mined at a profit mines (located deep within earth's crust)