Introduction to Minerals And you thought you were finished with chemistry

Photos of really cool places!  As we study rocks and minerals, remember these spectacular sites  Think about how they formed  Travel and ask questions!

Why should we care?  Salar de Uyini, Bolivia  World’s largest salt flat

Antelope Canyon, AZ

Zhangye Danxia Landform, Gansu, China

Fly Geyser, NV

Naica Mine, Mexico

What is a mineral? 1. Naturally occurring 2. Homogeneous solid 3. Definite, but generally not fixed, composition 4. Ordered atomic arrangement 5. Inorganic processes

Mineral Examples: How are compounds related to minerals? 3. Definite composition: SiO 2 ORFeS 2

Mineral Crystal ShapesCrystal geometric arrangement 4. Crystalline: 3D periodic arrays of precise geometric arrangement of atoms  Cut on the solid lines and fold on the dotted lines

Mineral or Not? At your table discuss whether or not the following materials are minerals. Be ready to justify your answers!  Snowflake  Coal  Rock salt  Window glass  Graphite  Oxygen

Mineral or Not…answers  Snowflake - Mineral Snowflake  Coal - Not  Table salt - Mineral  Window glass - Not Window glass  Graphite – Mineral  Oxygen- Not

How do minerals form?  There are four ways that minerals form: 1.Crystallization within magma (i.e. tourmaline, olivine, quartz, feldspar) 2.Precipitation from solution (salt flats) 3.Changes in pressure or temperature 4.Formation from hydrothermal solutions

How are minerals classified?  4,000 known minerals  International Mineralogical Association uses chemical composition to classify minerals  8 mineral classes that are categorized by their anion group

8 mineral classes 1. Silicate (SiO 2 ) Silicate (SiO 2 ) 2. Carbonate (CO 3 ) Carbonate (CO 3 ) 3. Sulfate (SO 4 ) Sulfate (SO 4 ) 4. Halide (F, Cl, I, Br are most common) Halide (F, Cl, I, Br are most common) 5. Oxide (usually a single O or OH) Oxide (usually a single O or OH) 6. Sulfide (S is usually bonded to a metal = ores) Sulfide (S is usually bonded to a metal = ores) 7. Phosphate (AO 4 where A can be P, Sb, As, V 8. Element Element

How do you identify minerals?  Geologists rely on several simple tests to identify minerals.  These are based on physical and chemical properties.  How would you use the 8 identifying properties to identify the minerals at your table?

8 Identifying Properties: 1.Color: This is the most noticeable characteristics of a mineral and the least helpful - This is determined by the presence of trace elements in certain compounds. Ex: Quartz: these are all the same

2.Luster: The way that a mineral reflects light from its surface. - Described as Metallic or Non-Metallic - Metallic – Reflect light like Gold, Copper, Silver - Non-Metallic – Calcite, Gypsum, Sulfur

Non-Metallic Luster continued… Most common Non-metallic Luster Descriptions: 1. Adamantine = brilliant like a polished diamond 2. Vitreous = glassy, like glazed porcelain or quartz 3. Resinous = yellow, dark orange, or brown like tree sap 4. Pearly = Exhibiting a luster similar to the inside of a mollusk shell or shirt buttonluster 5. Silky = minerals that have a very fine fibrous structure 6. Earthy = dull, little reflection

3.Texture: Describes how a mineral feels to the touch. - Words to describe: Smooth, Rough, Ragged, Greasy, Glassy. SmoothRough

4.Streak: The color of a mineral when it is broken up or in powdered form. - Usually rubbed against a porcelain plate, which leaves a powder behind. - Sometimes the external color doesn’t match streak color. - Streak hardly ever changes, even though the colors of a mineral do Pyrite: Streaks greenishGold: Streaks yellow

5.Hardness: a measure of how easily a mineral can be scratched. - Measured on the Mohs Hardness Scale – Ranges from 1 – 10 1 = Softest 10 = Hardest Talc = 1 Diamond = 10

NameHardness Hardness of Common Objects Talc1 Softest Gypsum2 Scratched by Fingernail Calcite3 Scratch by Penny Fluorite4 Scratched by Nail Apatite5 Scratched by Glass Feldspar6 Scratched by Steel File Quartz7 Topaz8 Scratches quartz Corundum9 Scratches Topaz Diamond10 Hardest – Scratches Everything Mohs Hardness Scale

6.Cleavage and 7. Fracture: How a mineral will break. - Cleavage – a mineral that splits relatively easily and evenly along one or more flat planes. - Fracture – Minerals that break with rough or jagged edges. Cleavage Fracture

8. Special Properties: Magnetic, odor, reacts to an acid, Tastes like salt, fluoresces, double refraction, Magnetite = Magnetic Sphalerite = Smells like rotten eggs Calcite = Reacts to HCL

Double Refraction- Calcite