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2. OBJECTIVES: Define a mineral. Describe how minerals form. Identify the most common elements in Earth’s crust. VOCABULARY mineral, crystal, magma and silicate

3. Facts about Minerals: Earth’s crust is composed of about 3000 minerals. Minerals play a role in forming rocks and shaping Earth’s crust Calcite is the mineral that forms the 2 million limestone blocks that make up the Great Pyramid in Egypt. Calcite is the primary mineral in the marble that makes up the Parthenon in Greece. Kingdoms have waged wars over silver and gold.

4. ?? ?? ?? ?? What is a Mineral ? Answer: A mineral is a naturally occurring, inorganic solid with a specific chemical composition and a definite crystalline structure.

5. Let’s Examine this definition: Naturally occurring and Inorganic. Naturally occurring – means it is formed in nature. Inorganic – means that it doesn’t contain carbon and that it was never a living breathing organism. Using your computers find the chemical formula for table salt (halite) and sugar (sucrose). Which of these is considered a mineral and which is not?

6. Let’s Examine this definition: Solids with Specific Compositions. Solids– have a definite shape and a definite volume. Specific Compositions – Each mineral has a chemical composition unique only to that mineral ! (FYI: With some crystals, the chemical composition may vary ….but must stay within a close range.) Can a liquid or a gas be mineral (based upon the criteria we’ve examined thus far? The mineral Olivine may have variable amounts of iron and magnesium atoms….but the ratio of iron and magnesium atoms to the total amount of silicon atoms is always the same.

7. Let’s Examine this definition: Definite Crystalline Structure. The atoms in minerals are arranged in a repeating geometric pattern. Solids with repeating geometric patterns are called crystals. Cubic Tetragonal Hexagonal Orthorhombic Monoclinic Triclinic Page 78 - text

8. Minerals From Magma: Minerals can form from the cooling of magma. Magma – the molten material found beneath Earth’s surface. If the magma cools slowly (within the Earth’s interior), the atoms arrange themselves to form large crystals. If the magma reaches air or water and cools quickly (Earth’s exterior), then the atoms form small crystals.

9. ?? ?? ?? ?? Of the 3000 known minerals, how many make up 90% of the Earth’s crust ? Answer: 10

10. ?? ?? ?? ?? What is the most common element in Earth’s crust? Answer: Oxygen Fact: About 90 known elements are found in Earth’s crust.

11. ?? Minerals are compounds made up from a combination of elements. Minerals that contain Oxygen and Silicon (and usually one or more other elements are known as Silicates.

12. ?? Silicates make up about 96% of the minerals found in Earth’s crust. The most common silicates are: feldspar and quartz. Silicates form a pyramid shaped structure called a tetrahedron.

13. ?? Silica tetrahedrons can combine in many ways, including: Single Chains Double Chains Sheets

14. Other Mineral Groups: Carbonates Carbonates are minerals composed of one or more metallic elements with the carbonate “compound” -CO 3 Examples: Calcite, Dolomite, and rhodochrosite. (Carbonates are primarily found in limestone, coquina, and marble.) Some carbonates are known for their distinctive colors. Page 83 - text

15. Other Mineral Groups: Oxides Oxides are compounds of oxygen and metal. Examples: Hematite, Fe 2 O 3, and magnetite, Fe 3 O 4, are common oxides and good sources of iron. Page 83 - text

16. Other Mineral Groups: Oxides Oxides are compounds formed from a metal and oxygen. Examples: Hematite Fe 2 O 3 Magnetite Fe 3 O 4. Page 82- 83 text

17. Section 4.2 : Identifying Minerals Mineral Identification Geologist use several test to identify minerals based upon the minerals chemical and physical properties. Pages 84-89 : text Question: Why do you think it’s best to have more than one test to identify a mineral?

18. Section 4.2 : Identifying Minerals Mineral Identification Geologist use several test to identify minerals based upon the minerals chemical and physical properties. 1 – COLOR (This is the least reliable identification test.) Some minerals can be found in several colors. “Trace” elements can cause color variations among minerals. (See the bottom of page 84 for an example of color variations in the mineral quartz.) Pages 84-89 : text

19. Section 4.2 : Identifying Minerals Mineral Identification Geologist use several test to identify minerals based upon the minerals chemical and physical properties. 2 – Luster The way that a mineral reflects light is referred to as luster. Luster is often described as metallic (shiny) or nonmetallic (dull). Pages 84-89 : text

20. Section 4.2 : Identifying Minerals Mineral Identification Geologist use several test to identify minerals based upon the minerals chemical and physical properties. 3 – Texture Texture describes how a mineral feels to the touch. Example: Smooth, rough, greasy, soapy, or glassy. Pages 84-89 : text

21. Section 4.2 : Identifying Minerals Mineral Identification Geologist use several test to identify minerals based upon the minerals chemical and physical properties. 4 – Streak Scratching a mineral against an unglazed porcelain plate will often leave an identifying powder or “streak”. Streak is the color left by a mineral when it is broken up. Pages 84-89 : text

22. Section 4.2 : Identifying Minerals Mineral Identification Geologist use several test to identify minerals based upon the minerals chemical and physical properties. 5 – Hardness Hardness is a measure of how easily a mineral can be scratched. German geologist Frederick Mohs developed a scale for mineral hardness that is still used today. Pages 84-89 : text Page 86 - textbook

23. Section 4.2 : Identifying Minerals Mineral Identification Geologist use several test to identify minerals based upon the minerals chemical and physical properties. 6 – Cleavage and Fracture A mineral that splits evenly and evenly along one or more planes is said to have “cleavage”. Minerals that break in a rough or jagged manner are said to have “fracture”. Minerals that have cleavage tend to break where the bonds between atoms are weak. Pages 84-89 : text

24. Section 4.2 : Identifying Minerals Mineral Identification Geologist use several test to identify minerals based upon the minerals chemical and physical properties. 7 – Density and Specific Gravity The density of a substance if found by it’s mass/volume ratio. Density = mass / volume. Specific Gravity is a comparison of a substances density to the density of water. Pages 84-89 : text

25. Section 4.2 : Identifying Minerals Mineral Identification Sometimes “special properties” can be used to identify minerals: Iceland Spar – Refracts (bends) light in two directions. Magnetite - Attracts metals Sphalerite – Smells like rotten eggs when it’s scratched. Pages 84-89 : text

26. Section 4.2 : Identifying Minerals Mineral Identification Pages 84-89 : text Ores – An ore is a mineral that contains a useful substance that can be mined at a profit. – Examples of ores include Hematite, which contains the element iron and bauxite, which contains the element aluminum.

27. Section 4.2 : Identifying Minerals Mines Pages 84-89 : text – Ores are removed by underground mining or from large, open-pit mines. – When a mine is excavated, unwanted rock and dirt, known as waste material, are dug up along with ore. – If the cost of separating the waste material becomes higher than the value of the ore itself, then the mineral will no longer be classified as an ore because it would no longer be economical to mine it. – The classification of a mineral as an ore may also change if the supply of or demand for that mineral changes.

28. Section 4.2 : Identifying Minerals Mineral Identification Pages 84-89 : text Gems Gems are valuable minerals that are prized for their rarity and beauty. Gems such as rubies, emeralds, and diamonds are cut, polished, and used for jewelry. In some cases, the presence of trace elements can make one variety of a mineral more colorful and thus more prized than other varieties of the same mineral.