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This 6 page Class Notes was uploaded by Shannon zarrilli on Wednesday January 27, 2016. The Class Notes belongs to GEO 101 at University of Alabama - Tuscaloosa taught by Dr. Natasha T. Dimova in Fall 2016. Since its upload, it has received 68 views. For similar materials see The Dynamic Earth in Geology at University of Alabama - Tuscaloosa.
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Date Created: 01/27/16
Geo 101 Chapter 3 Patterns in nature minerals Outline: 1. Minerals and why we are interested in them? 2. Some chemistry knowledge we need to know when we talk about minerals 3. Crystal’s structure 4. Mineral properties 5. Mineral classification Minerals: -Make up the rocks and sediments -Raw materials for manufacturing chemicals for industrial use - in building machine/ tool parts -Energy resources e.g. uranium - Jewelry *Minerals are the building blocks of rocks Mineral- naturally occurring solid, formed by geological processes, crystalline structure, defined inorganic composition Naturally occurring: • Minerals that are produced in nature, NOT man-made! • Man-made minerals are called “synthetic minerals” Solid: • own shape • Difference with liquids and gases which take the shape of the container they are poured into! Crystalline structure • The atoms that the minerals are made of are organized in a specific way. • This specific way is called pattern • Geologists also use the term crystalline lattice **Pattern and crystalline lattice are the same terms! Defined inorganic chemical composition • chemical formula that can be written to express the chemical composition of a mineral • The chemical composition is inorganic, e.g. sodium (Na), potassium (K), calcium (Ca) etc. • In contrast, organic molecules are built mostly of carbon (C ), hydrogen (H), and oxygen (O); for example methane (CH , 4 C2H 5H) Composition of minerals Elements- building block of minerals, more than 100 elements Atoms- smallest particles of matter Rocks/sediments Minerals molecules/atoms (diff. chem elements) Atomic structure: nucleus- protons(positive) and neutrons (no charge) Electrons- surrounded nucleus( negative), located in the energy levels-shells **structure of the atom Chemical bonds _Ionic bond- based on connection between oppositely charged ions Ion- atom that has gained or lost electrons Cation- atom that has lost electron has positive charge. For example: 2+ 3+ +, Fe , Al , K Anion- atom (or group of atoms) that have gained electrons (s), i.e. 2- 2- - - 3- with extra negative charge. For example: SO 4 ; CO 3 Cl , NO , 3O 4 etc. Composition of Minerals: 2. Covalent bonding- Atoms share electrons to achieve electrical neutrality Covalent bounding: example methane (CH ) 4 3.Metallic bonds: Electrons migrate among atoms, good conductivity Example: copper & gold 4. van der Waals bonds: Weak attractive force between electrically neutral atoms/molecules (no electrons available to form bonds) Example: graphite Chemical reaction: ex. Methane combustion • Process that involves breaking chemical bonds and building new ones Structure of minerals Minerals: orderly array of atoms bonded to form a crystalline structure Different atoms will pack into different arrangements Orderly arrangement givens minerals symmetry Example- Salt NaCl Polymorphs: minerals with the same chemical composition but different atomic arrangement Diamond: atoms arranged in tethrahedra; strong bonds between them. Graphite: atoms arranged in hexagonal sheets, which are connected with week bonds. Identify minerals- observing, performing simple tests Primary Diagnostic Properties- System of several physical properties are used to identify hand samples of minerals Diagnostic properties 1. Crystalline Form-External expression of mineral’s internal structure (i.e. how atoms are arranged); Garnet (dodecahedron), Pyrite (cubic) 2. Luster Appearance in reflected light 2 major categories: Metallic, Nonmetallic 3. . Color Generally unreliable for mineral ID; variable due to impurities in mineral chemistry Colorations of minerals produce gemstones Quartz Ex. Corundum, Blue = Sapphire (iron), Red = Rubies (chromium) Beryl, Green = Emerald (chromium), Blue= Aquamarine (iron) 4. Streak Color of a mineral in its powdered form Obtained by scratching the mineral on an porcelain plate Can be different from color because in powder form, the effect of impurities is reduced 4. Hardness Resistance of mineral to abrasion or scratching All minerals are compared to standard scale Mohs Hardness scale 5. Cleavage Tendency to break along planes of weak bonding Produces flat, shiny surfaces 6. Fracture Absence of cleavage when a mineral is broken 7. Specific Gravity Weight of mineral divided by the weight of an equal volume of water Avg. = 2.7 g/cm3 Other: magnetism, reaction to hydrochloric acid, double refraction, taste, smell Minerals - Nearly 4000 different minerals Rock-forming minerals Only a few dozen members Made of the most common elements in the Earth’s crust Mineral groups: Silicates (SiO 2: most important mineral group – Very abundant due to large percentage of silicon and oxygen in the Earth’s crust – Silicon-oxygen Tetrahedron: fundamental building block – Four oxygen ions surrounding a smaller silicon ion Tetrahedral Forms (combos) By combining the SiO t2trahedra together in different ways, we can make different minerals! Categories of Silicate SiO2 Minerals Mafic: Simpler SiO 2tructure Dark colored; more dense Contain iron and magnesium Felsic: More complex SiO s2ructure Light colored; less dense No iron or magnesium Non-Silicate Minerals: less than 10% of Earth’s Crust Many non-silicate minerals have important economic valueHematite (Fe O ,2ox3de mined for iron ore) Halite (NaCl, halide mined for salt) Sphalerite ((Zn,Fe)S, sulfide mined for zinc ore) Native copper (Cu, mined) Carbonates (CO , mi3ed for cement)
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