GEO 102 Lecture 8Outline of Last Lecture I. What the earth is made of Outline of Current Lecture II. How to ID a mineral III. How geologists ID a mineralIV. Families of minerals and how they formV. Types of rocksCurrent LectureHow do you ID a mineral?-Properties-mass-hardness-luster-shape-cleavage-Etc…like in your lab section-Don’t be fooled by color, size, etc…How do geologists ID a mineral?-In the field we use the same techniques you do in your lab section-In the lab we use other propertiesThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.-chemical composition-structure-Light bends according to the way a substance changes the light waves-Diffraction is the way a wave is interfered with by a materialFamilies of Minerals-silicates: largest group-Harder minerals-Common-Quartz, feldspar, garnet…-Some subfamilies are important-Clay minerals-carbonates: (carbon + Oxygen) “soft rock” not near as common as silicates but are abundant above the Earth. Made by animals and humans and almost always form on theEarth’s surface.-Softer-Less common-Calcite, aragonite (sea shells)Mineral Groups-carbonates-CaCO3 and variants-Important for deciphering earth history-Often produced by organisms-Coral, sea shells, microrganisms, etc…-Much of Alabama is made of carbonatesPractical Mineralogy-Only a few minerals make up most of the Earth’s solid materials:-Quartz-potassium Feldspar-Plagioclase Feldspar-Olivine-Pyroxene-Amphibole-Mica-CalciteHow do they form?-Several ways…-from cooling magma-from solution in water-solution in other fluids-in or around living cellsRocks-Igneous rocks (rocks that form from magma-intrusive. Rocks that form from lava-extrusive)-From magma or lava-Metamorphic-Altered through heat and/or pressure-Sedimentary-Reformed bits of other rocks, broken down or from
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