105_03-minerals_part_2 - Minerals Criteria Mineral or not...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Minerals Criteria: Mineral or not? Solid Naturally occurring Definite composition Crystalline structure Water Halite Cubic zirconia Ice Chemical Chemical Composition – Shown by a chemical formula such as NaCl (Halite) or SiO2 (Quartz) Minerals More More than 3,500 identified – Less than 25 are common as rock forming minerals – They are composed of the most abundant elements found in the crust Top 8 list of elements in crust 1. O, Oxygen 2. Si, Silicon 3. Al, Aluminum 4. Fe, Iron 5. Ca, Calcium 6. Na, Sodium 7. K, Potassium 8. Mg, Magnesium All others 46.6% by weight 27.7% 8.1% 5.0% 3.6% 2.8% 2.6% 2.1% 1.5% Top 8 elements make up 98.5% of the Earth’s crust Mineral Groups Silica Tetrahedra O2 Si4+ + Si4 - O2 - O2 O2 O2 - - O2 O2 O2 - 1 Mineral Groups Single Chain Silicates Pyroxene Silicates Silicates – Combo between silica tetrahedra and other ions – ~1/3 of all known minerals – 95% of Earth’s crust! Double Chain Silicates Sheet Silicates mica Sheet Silicates Mineral Groups Carbonate Carbonate Minerals – Contain the negatively charged carbonate ion (CO3)-2, which bonds with a positively charged calcium (Ca) ion – Calcite (CaCO3) – Dolomite [CaMg(CO3)2 2 Mineral Groups Other Other Mineral Groups – – – – Oxides (Fe2O3) Sulfides (PbS) Sulfates (CaSO4·2H2O) Halides (NaCl) Mineral Identification Physical Physical properties of minerals – All minerals have characteristic properties Galena, a lead sulfide – Determined by the internal structure and chemical composition – Most properties are constant, but some variation exists, especially in color Halite, a halide Gypsum, a sulfate Mineral Identification Color Color – impurities – chemical formula Quartz Mostly not characteristic Mineral Identification Luster Luster (quality of reflected light) – Metallic – Nonmetallic Calcite Glassy Glassy Earthy Earthy Silky Silky Pearly Pearly Waxy Waxy Dull Dull Mineral Identification Crystal Crystal Form – Can occur in a variety of shapes which reflect the orderly internal arrangement of atoms. Mineral Identification Crystal Crystal Form – Reflects internal geometry and composition – Perfect crystals are rare, but may be useful in identification 3 Mineral Identification Perfect crystals are rare, but may be useful in identification Mineral Identification Perfect crystals are rare, but may be useful in identification Mineral Identification Cleavage Cleavage – Some minerals break along very straight planes Mineral Identification Cleavage Cleavage and Fracture Cleavage: Cleavage: mineral breaks along planes that have weak bonds Fracture: Fracture: mineral breaks along irregular surfaces when no weak planes exist Mica: one excellent cleavage 4 Mineral Identification Mineral Identification Hardness Hardness – Internal structure and strength of bonds – Based on the Mohs scale from 1 to 10 ShellShell-shaped, conchoidal fracture of quartz Quartz has a hardness of 7 and shows conchoidal fracture Mineral Identification Hardness Mineral Identification Streak Mineral Identification Streak Streak – Powdered minerals are sometimes a different color than their solid form – Scrape a mineral on a porcelain streak plate Hematite 5 Mineral Identification Specific Specific Gravity (Density) Smell Smell Taste Taste (Halite) Striations Striations (Plagioclase feldspar) Attracted Attracted to magnets (Magnetite) Double Double refraction (Calcite) Mineral Identification Chemical Chemical tests – reaction to HCl Plagioclase striations How do we really do it??? Chemical Chemical tests X-ray diffraction Thin Thin sections Minerals The Building Blocks of Rocks Chapter 3 6 ...
View Full Document

This note was uploaded on 05/18/2011 for the course GEOL 105 taught by Professor Jack during the Spring '08 term at University of Louisiana at Lafayette.

Ask a homework question - tutors are online