9-2 - Patterns in Nature: Minerals Minerals The “building...

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: Patterns in Nature: Minerals Minerals The “building blocks” of rocks, and hence, of The Earth. More than 4,000 are known. Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 5: Patterns in Nature: Minerals Mineral Definition Geologic definition of a mineral is specialized: Naturally occurring. Solid. Formed geologically. Definite chemical Definite composition. Crystalline structure. Inorganic. Gypsum Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 5: Patterns in Nature: Minerals Rocks Rocks are Earth materials made from minerals. Most rocks have more than one kind of mineral. Example: Granite Potassium feldspar. Quartz. Hornblende. Some are monomineralic. Limestone (Calcite). Rock salt (Halite). Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 5: Patterns in Nature: Minerals Crystalline Structure Atoms in a mineral are specifically ordered. Crystalline structure based on atomic patterns. Crystalline Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 5: Patterns in Nature: Minerals Polymorphs Same composition but different crystal structure. Diamond and graphite are carbon polymorphs (C). Diamond Diamond – Strong covalent bonds; hardest mineral. Graphite – Weak Van der Waals bonds; softest mineral. Diamond Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Graphite Chapter 5: Patterns in Nature: Minerals Physical Properties Common properties: Color. Streak. Luster. Hardness. Specific gravity. Crystal habit. Crystal form. Fracture. Cleavage. Needle-like crystal habit Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 5: Patterns in Nature: Minerals Color Color is diagnostic for some minerals. Some minerals may exhibit a broad color range. Olivine is olive green. Azurite is always blue. Quartz (Clear, white, yellow, pink, purple, gray, etc). Color varieties often reflect trace impurities. Color Quartz – Many colors Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Malachite – Always green Chapter 5: Patterns in Nature: Minerals Streak Color of a mineral crushed on unglazed porcelain. Streak is often a useful diagnostic property. Hematite – Red-brown streak Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 5: Patterns in Nature: Minerals Hardness Scratching resistance of a mineral. Scratching Hardness compared to the Mohs Hardness Scale. 1. 2. 3. 4. 5. 6. 7. 7. 8. 9. 10. Talc, Graphite Gypsum Fingernail 2.5 Calcite Copper Penny 3.5 Fluorite Apatite Glass - Steel 5.5 Orthoclase Orthoclase Steel File 6.5 Quartz Topaz Corundum Diamond Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 5: Patterns in Nature: Minerals Crystal Habit Crystal habit is the ideal shape of crystal faces. Ideal growth requires ideal conditions. Ideal Many terms are used to describe habit. Many Cubes Dodecahedra Octahedra Compound Forms Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Blades Rhombohedra Hexagonal Prisms Tetragonal Prisms Chapter 5: Patterns in Nature: Minerals Cleavage Tendency to break along planes of weakness. Tendency Cleavage produces flat, shiny surfaces. Described by number of planes and their angles. Sometimes mistaken for crystal habit. Sometimes Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 5: Patterns in Nature: Minerals Mineral Compositions Only about 50 minerals are abundant. Only 98.5% of crustal mineral mass is from 8 elements. Oxygen Oxygen Silicon Aluminum Aluminum Iron Calcium Calcium Sodium Sodium Potassium Potassium Magnesium Magnesium All others All O Si Al Al Fe Ca Ca Na Na K Mg Mg Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak 46.6% 27.7% 8.1% 5.0% 3.6% 2.8% 2.6% 2.1% 1.5% 74.3% of crustal minerals !!! Chapter 5: Patterns in Nature: Minerals Mineral Classes Minerals are classified by their dominant anion. Silicates Silicates SiO24SiO 4- Rock-forming mins Rock-forming Oxides Sulfides Sulfates O2SSO42- Magnetite, Hematite Magnetite, Pyrite, Galena Pyrite, Gypsum Gypsum Halides Halides Carbonates Cl- or FCl CO32- Fluorite, Halite Fluorite, Calcite, Dolomite Calcite, Native Elements Cu, Au, Malachite (Carbonate) Fluorite (Halide) Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak C Copper, Graphite Native Copper Chapter 5: Patterns in Nature: Minerals Silicate Minerals Silicate Silicates are know as the rock-forming minerals. Silicates They dominate the Earth’s crust. They Oxygen and silicon… Oxygen Make up 94.7 % of crustal volume, and... 74.3 % of crustal mass. 74.3 Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 5: Patterns in Nature: Minerals Silicate Minerals Silicate The anionic unit is the silica tetrahedron. 4 oxygen atoms are bonded to 1 silicon atom (SiO44-). Silicon is tiny; oxygen is huge. Silicon Earth: Portrait of a Planet, 3rd edition, by Stephen Marshak Chapter 5: Patterns in Nature: Minerals ...
View Full Document

Ask a homework question - tutors are online