Minerals Page 191

1. MineralsPage 191 SC Standard 8-3.5 Summarize the importance of minerals, ores, and fossil fuels as Earth resources on the basis of their physical and chemical properties.

8. Minerals • A naturally occurring, inorganicsolid that has a crystal structure and defined chemical composition. • More than 4000 minerals. • Only about 100 are common.

10. Minerals • Must have FIVE characteristics to be classified as a mineral: • Naturally occurring • Inorganic • Solid • Crystal structure • Defined chemical composition

11. What_Are_Minerals_.asf

12. 1) Naturally Occurring • Must occur natural (not man made) • Cement and brick consist of natural substances, but they are made by humans. 2) Inorganic • Can not come from materials that were once living things. • Coal forms naturally, but it is made from plant and animal remains.

13. 3) Solid • Must have a definite volume and shape. • A solid keeps its shape. (demo on volume) • It always contains certain elements in definite proportions. 4) Crystal shape • Atoms are arranged in a repeated, orderly pattern. 5) Definite Chemical Structure

14. What are an Element and a Compound? • Element: a substance composed of a single atom. • Compound: two or more elements are chemically combined. (H2O) • ALL minerals are compounds. (exception are some metals ex. Gold, silver etc..)

15. Identifying Minerals • Each mineral has its own specific Physical properties that can be used to identify it. -Hardness - Density -Color - Crystal System -Luster - Cleavage and Fracture -Streak - Special properties The_Physical_Properties_of_Minerals.asf

16. 1. Hardness • Mohs hardness scale • Used to rank 10 minerals from softest to hardest • Invented by Austrian mineral expert

17. Mohs Hardness Scale MineralRatingTesting Method Talc 1 Softest known mineral. Scratched by fingernail Gypsum 2 A fingernail can easily scratch. Calcite 3 A fingernail cannot scratch, but a penny can. Fluorite 4 A steel knife can easily scratch it. Apatite 5 A steel knife can scratch it. Feldspar 6 Steel knife cannot scratch it, it can scratch glass Quartz 7 Can scratch steel and hard glass Topaz 8 Can scratch quartz Corundum 9 Can scratch topaz Diamond 10 Hardest known mineral. Can scratch all other substances.

19. 2. Color • Can be easily observed. • Some minerals maintain the same color. • Azurite is always blue. • Some minerals can occur in a variety of colors. • Calcite comes in many colors (figure 5 page 195)

20. 3. Streak • The streak of a mineral is the color of it’s powder. • Observe streak by rubbing a mineral against a piece of tile. • Streak color and mineral color are often different. • Streak color does not vary!!

22. 4. Luster • Luster is the term used to describe how a mineral reflects light from its surface. • Words used to describe luster are listed below: • Shiny - Earthy • Glassy - Pearly • Waxy - Metallic

23. 5. Density • Density is MASS in any given space (VOLUME). • You can compare the density of two minerals by picking them up. • Minerals of the same size will have a different weight. • To find density, you need to know the volume and mass of a mineral. (triple beam balance and a graduated cylinder or beaker)

24. 6. Crystal Systems • Crystals of minerals grow atom by atom. • Crystals are classified by the number and angles of the faces. • The 6 groups are listed below: • Cubic - Orthorhombic • Hexagonal - Monoclinic • Tetragonal - Triclinic

25. 7. Cleavage and Fracture • A mineral that splits easily along flat surfaces has the property called cleavage. • Cleavage depends on how the atoms are arranged. • Fracture describes how a mineral looks when it breaks apart in an irregular way.

26. 8. Special Properties • Minerals that glow under ultra violet light have a property called fluorescence. • Magnetism also occurs naturally in some minerals. • Some minerals are radioactive • Some minerals react to acid. (Chemical properties)

27. Chemical Properties • Some minerals react to acid. • Some mineral will burn

28. 3 WAYS MINERALS FORM • Meltedrock material in Earth - Magma • Evaporation – as a solution evaporates, minerals will crystallize. • Precipitation – water can hold only so much solution, any extra • “falls out” leaving behind • solids.

30. Gemstones • A hard, colorful mineral that has a brilliant or glassy luster. • Valued for their color, luster and because they are rare. • Once cut and polished it is called a gem. • Gems are mainly used for • jewelry and decoration.

31. Metals • Some minerals are the sources of metals such as: • aluminum, iron, copper and silver • Metals are useful because they can be stretched into wire, flat sheets or molded without breaking.

32. Ores • ORE - A rock that contains a metal or an economically useful mineral. • Most metals do not occur in pure form. • They occur as a mineral that is a combination of that metal and other elements.

33. Locating Ores • Prospecting – The action of searching or prospecting for an ore deposit. • Geologist prospect by looking for certain features on the Earth’s surface. • Once the ore is found, it must be mined or removed from the earth. • Three types of mines: • Strip mines, open pit mines and shaft mines.

34. Smelting • After miners remove ore from a mine, smelting is necessary to remove the metal from the ore. • The ore is melted to separate the useful metal from the other elements the ore contains.

35. Other useful minerals • Talc – used for talcum powder • Quartz – used in making glass • Gypsum – used to make cement and stucco