Chapter 5.2 – 5.4 Minerals Earth Science 1

Minerals Mineral – A mineral is any material that… 1. Is a Solid 2. Is Inorganic 3. Is Naturally Occurring 4. Has a Fixed Chemical Composition 5. Atoms Are Arranged in Orderly Pattern 2

Minerals and How They Form

Critical Thinking #1 Is water a mineral? Why or why not? Is a seashell a mineral? Why or why not? Is plastic a mineral? Why or why not? 4

Minerals Crystal Form Many minerals possess a crystalline form – regular geometric shapes with smooth faces 5

Crystal Structures

Two Types of Minerals Silicates Contains Silicon (Si) and Oxygen (O) 90% of Earth’s Crust 7

Two Types of Minerals Non-Silicates No Combination of Silicon (Si) and Oxygen (O) Common Non-Silicates Carbonates (Carbon + Oxygen) Oxides (Iron or Aluminum + Oxygen) Sulfates (Sulfur + Oxygen) 8

Identifying Minerals Color Easily observed, but… the same minerals can vary in color ex: Sulfur = Yellow Quartz = Clear, Purple, Green, Red etc. 9

Colors of Quartz Clear Quartz Amethyst Rose Quartz

Critical Thinking #2 Is color a good way to identify minerals? Why or why not? 11

Identifying Minerals Streak The color of a mineral in powdered form More reliable than color 12

Identifying Minerals Luster How a mineral reflects light Metallic – reflective, silver or gold color, found in most metals 13

Identifying Minerals Nonmetallic Luster – not reflective Vitreous – glassy Silky – fibrous Resinous – yellow, dark brown Waxy Pearly Earthy – dull, looks like clay 14

Identifying Minerals Cleavage Fracture (No Cleavage) Minerals break along a smooth, flat surface Fracture (No Cleavage) Minerals break unevenly along an irregular surface 15

Critical Thinking #3 From your experience, do most minerals fracture or demonstrate some type of cleavage? Explain your reasoning. 16

Identifying Minerals Hardness Mohs Scale – (1-10) Softest to Hardest 1- Talc (Softest) 10 – Diamond (Hardest) 17

Identifying Minerals Two More Methods Malleability: How well the mineral can be hammered into shape. Ductility: How well the material can be drawn out into a thin wire without crumbling. 10/25/13

Critical Thinking #4 Based on the hardness scale, how would the scale need to be adjusted if a new mineral was discovered that was harder than a diamond? 19

Identifying Minerals Special Properties Fluorescence – glow under ultraviolet radiation Chemical Reactions – fizz when combined with acid Optical Properties – double image formed Magnetism – ex: Magnetite is magnetic Taste ex: Halite (salt) tastes salty Radioactivity – contains radium or uranium 20

Critical Thinking #5 Which special properties tests would be difficult to conduct? Which would be easy? 21

Major Silicates: Quartz Glassy or greasy luster Colorless or white (some variations) Conchoidal or irregular fracture Mohs scale 7 Found in granite and other rocks

Feldspars Two directions of cleavage Hardness scale 6 Pearly luster Contains aluminum plagioclase orthoclase

Other Silicates amphibole pyroxene mica olivine

Carbonates limestone marble calcite

Oxides and Sulfides magnetite hematite Pyrite (fool's gold)

Archimedes Principle If an object can displace the volume of water equal to the weight of the object, it will float.