1. MINERALS There are about 3000 different minerals in the Earth’s crust!

2. 3 characteristics of minerals 1)Minerals are naturally occurring, inorganic solids 2)Each has a specific chemical composition 3)Each has a definite crystalline structure

3. Naturally Occurring Inorganic Solids Minerals are formed by natural processes –Synthetics and substances developed in labs are NOT minerals Inorganic means they are not alive and have never been alive –Sugar is not a mineral—it is harvested from plants –Coal is not a mineral—it is from decayed living things

4. Why is a natural emerald considered to be a mineral, but a synthetic emerald is NOT considered to be a mineral? Synthetic is not natural!

5. Why is halite (rock salt) considered to be a mineral, while rock candy (crystallized sugar) is NOT considered to be a mineral? Sugar comes from a plant! Rock salt was never alive!

6. Solids with a Specific Chemical Composition Minerals are not liquids or gases Minerals are a specific element or compound –The chemical composition of a specific mineral is in a well-defined range

7. CRYSTAL A solid in which the atoms are arranged in repeating patterns Easy to see the crystal system if the mineral is grown in an open space and grows into one large crystal –RARELY HAPPENS The crystal system may be not obvious is the crystal grew in a restricted space –MORE COMMON

9. Why is a gypsum crystal considered to be a mineral, but a typical rock you would pick up outside would NOT be considered to be a mineral? Gypsum has a definite crystal structure, but a rock does not!

10. Sources of Minerals 1)Magma: molten material found beneath Earth’s surface –Density differences force magma upward into cooler layers of Earth’s interior, where the magma cools –The compounds in the magma no longer move freely and they begin to interact chemically to form minerals –Rate at which the magma cools determines the size of the crystals

11. Sources of Minerals 2)SOLUTION Minerals precipitate (or drop out of) solutions that are supersaturated (or overfilled) or when water evaporates from a supersaturated solution.

12. Only 30 of the 3000 minerals in Earth’s crust are common The most common are referred to as rock- forming minerals because they make up most of the rocks found in Earth’s crust. About 90 known elements occur naturally in the Earth’s crust The vast majority of minerals are made up of the 8 most common elements.

13. MINERAL GROUPS Silicates Contain silicon and oxygen and usually one or more other elements 96% of the minerals in Earth’s crust Most common minerals: Feldspar & Quartz The bonds between the atoms determine mineral splits

14. MINERAL GROUPS Carbonates Minerals composed of one or more metallic elements with the carbonate compound (CO 3 ) Primary minerals in limestone and marble Some have distinctive colorations Examples: Calcite, dolomite, azurite, malachite

15. MINERAL GROUPS Oxides Compounds of oxygen and a metal Examples: Hematite, Magnetite (good sources of iron) and Uraninite (source of uranium) Other Mineral Groups Sulfides, sulfates, halides, and native elements

16. MINERAL IDENTIFICATION There are 7 ways minerals can be identified It is best to use a combination of tests rather than just one The 7 tests: Color, Luster, Texture, Streak, Hardness, Cleavage & Fracture, Density & Specific Gravity

17. COLOR Sometimes caused by trace elements or compounds within a mineral One of the least reliable clues to a mineral’s identity

18. LUSTER The way that a mineral reflects light from its surface Described as either metallic or nonmetallic –Metallic: Reflect light Gold, silver, copper, galena –Nonmetallic: Dull, pearly, waxy or silky Calcite, gypsum, sulfur and quartz Differences in luster are caused by differences in the chemical compositions of the minerals

20. TEXTURE How a mineral feels to the touch –Smooth, rough, ragged, greasy, soapy or glassy

21. STREAK The color of a mineral when it is broken up and powdered –A colored powdered streak is left behind by some minerals when they are rubbed across an unglazed porcelain plate –Sometimes does not match the mineral’s external color Pyrite (fool’s gold) leaves a greenish-black streak, while real gold leaves a yellow streak –A mineral’s streak rarely changes –Can only be used on minerals softer than a porcelain plate Cannot be used to identify all minerals

22. HARDNESS Measure of how easily a mineral can be scratched Mohs scale: Developed by the German geologist Friedrich Mohs –Scale in which an unknown mineral’s hardness can be compared to the known hardnesses of 10 minerals –Any mineral with a greater hardness than another mineral will scratch the softer mineral One of the most reliable tests

23. Moh’s Scale Hardness Examples: 1) A mineral that can scratch quartz would have a hardness > __________. 2)A mineral you could scratch with your fingernail would have a hardness < ___________. 3) Would Talc be able to scratch quartz? Why or why not?

24. CLEAVAGE AND FRACTURE A mineral that splits relatively easily and evenly along one or more flat planes has cleavage –Minerals that break into sheets have weak atomic bonds A mineral that breaks with rough or jagged edges are said to have fracture –Minerals that break unevenly or along jagged edges have tightly bonded atoms –Conchoidal fracture: Fracture with arclike patterns resembling clam shells (flint, chalcedony, obsidian)

25. CLEAVAGE VS. FRACTURE

26. DENSITY & SPECIFIC GRAVITY Density: mass per unit volume (D = m/V) –Pyrite = 5.2 g/cm 3 ; Gold = 19.0 g/cm 3 –Reflects the atomic weight and structure of a mineral Specific Gravity: The ratio of the weight of a substance to the weight of an equal volume of water at 4  C (39.2  F) –Most common measure of density used by geologists

27. SPECIAL PROPERTIES Double refraction: The refraction of a single ray of light into two rays creating two images Calcite also fizzes when it comes in contact with hydrochloric acid Magnetite: Naturally magnetic Sphalerite: Distinctive rotten egg odor when rubbed on streak plate (sulfide)

28. MINERAL USES Minerals are virtually everywhere Computers, cars, tv’s, desks, roads, buildings, jewelry, beds, paints, sports equipment, medicines, etc. USES OF TALC

29. ORES A mineral is an ORE if it contains a useful substance that can be mined at a profit –Hematite: Ore that contains IRON –Bauxite: Ore that contains ALUMINUM

30. MINES Ores that are located deep within the Earth’s crust are removed by underground mining Ores that are near Earth’s surface are obtained from large, open-pit mines –Waste material must be separated from the ore before the ore can be used If the cost of removing the waste is higher than the value of the ore then the mineral will no longer be classified as an ore and it is not economical to mine it –Classification of a mineral as an ore may if the supply of or demand for that mineral changes. If demand drops substantially, the mineral is no longer considered an ore

31. GEMS Valuable minerals that are prized for their rarity and beauty –The more rare, the more valuable –Trace elements can make one variety of a mineral more colorful and thus more prized than other varieties of the same mineral