Video Resource: https://drive.google.com/file/d/0BxOms4hIDvR3TmxEcHJWV2xzTkU/view Similarities of Rocks and Minerals •Inorganic compounds (non-living) •Both can be classified by their chemical composition. •Solids •Naturally formed •Found around the world in many of the same places on Earth Rocks •Most commonly classified by how they form. 1.Sedimentary 2.Metamorphic 3.Igneous •Composed of more than one mineral. •No definite chemical composition. •No definite crystal structure. Minerals In addition to being inorganic, solid, and naturally formed like rocks, minerals also have: •A definite chemical composition. (amounts of elements present) •A definite crystal structure. (unique arrangement of atoms/molecules) Mineral Identification – Important Vocabulary 1.Color (green, red, yellow, blue, etc.) 2.Streak (Color of the streak across a streak plate) 3.Luster (Metallic or Non-Metallic) 4.Hardness (Mohs Scale) 5.Density (Specific gravity) 6.Breakage Pattern (Cleavage and Fracture) Color •Many minerals have distinctive colors, but they come in a variety of hues. •Color should never be used as the only test for identifying a mineral. Streak •The color a mineral displays in a finely powdered form •Might be completely different from the color of the mineral itself •To determine the streak, rub the mineral across a piece of unglazed porcelain know as a streak plate. Luster •The way a mineral’s surface reflects light. •Two types of luster •Metallic – shiny like a metal •Nonmetallic – several kinds 1. Glassy - quartz 2. Pearly - talc 3. Greasy - graphite 4. Silky – gypsum 5. Resinous - sulfur 6. Adamantine - diamond Hardness •One of the most reliable ways to identify minerals •Compares the resistance of a mineral to being scratched by 10 reference minerals •Called the Mohs Hardness Scale •Named after Friedrich Mohs, a German mineralogist, who developed the scale in 1812 Density •Defined as the amount of matter per unit volume •Density = mass divided by volume •In minerals, the term specific gravity is used in describing density. In this way minerals can be compared and identified. Cleavage •Refers to the way some minerals break along certain lines of weakness in their structure Mica is a good example. Fracture •A description of the way a mineral tends to break •Some different types of fracturing 1. Conchoidal – smooth curve 2. Hackly – sharp jagged edges 3. Uneven – rough and irregular 4. Fibrous – shows fibers Gemstones Some minerals are cut to become precious gemstones. Comments are closed.
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Erik E. Mason
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