Unit 2 : Rocks and Minerals A. Atomic Structure 1. Elements – substance that cannot be broken down into simpler substances 2. Atoms – Smallest particle of matter that contains the characteristics of an element 3. Nucleus – Central region; contains; a. Protons – positive charge (+) b. Neutrons – no charge (0) c. Electrons – negative charge (­) that surround the atom’s nucleus B. Minerals 1. Naturally occurring, inorganic solid with an orderly crystalline structure and definite chemical composition 2. To be considered a mineral it must have the following characteristics: 3. Naturally occurring (forms naturally) 4. Solid substance 5. Orderly crystalline structure 6. Definite chemical composition 7. Generally inorganic 8. Properties of Minerals a. Color – Not a useful property b. Streak – color of a mineral in its powdered form c. Luster – how light is reflected from the surface d. Crystal form – visible expression of a mineral’s internal arrangement of atoms e. Hardness – measure of the resistance of a mineral being scratched i. Mohs scale – standard hardness scale 1 (softest) – 10 (hardest) f. Cleavage – tendency to cleave, or break, along flat, even surfaces g. Fracture – uneven breakage of a mineral h. Density – ratio of an object’s mass to its volume D = mass (m) / Volume (V) C. Rocks 1. Rock – any solid mass of mineral or mineral­like matter that occurs naturally as a part of our planet 2. most rocks are a mixture of different minerals 3. 3 groups of rocks a. igneous – a rock formed from by the crystallization of molten magma b. sedimentary – rock formed from the weathered products of pre­existing rocks that have been transported, deposited, compacted, and cemented c. metamorphic ​(meta = change, morph = shape) – rock formed by the changing pre­existing rock through heat and pressure D. Rock Cycle 1. rock cycle – continuous process that causes rocks to change 2. the forms of energy that drive the rock cycle include heat and mechanical Energy 3. involves interactions among the Earth’s water, air, and land 4. Stages a. magma forms when rock melts deep beneath the Earth’s surface b. when magma or lava cools and solidifies, igneous rocks form c. rocks at Earth’s surface are broken down into smaller pieces called sediments d. when sediments are compacted and cemented, sedimentary rocks form e. any type of rock that is changed by heat, pressure, or fluids becomes a metamorphic rock 5. deposition – when sediments are dropped due to an agent of erosion (water, wind, ice, or gravity) losing energy 6. compaction – process that squeezes or compacts sediments a. caused by weight b. pushes water out 7. cementation – takes place when dissolved minerals are deposited in the time space among the sediments