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The Stuff that Rocks are made of

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1 The Stuff that Rocks are made of
Minerals The Stuff that Rocks are made of PowerPoint Notes created by S. Koziol Date : 9/1/2013 Revised : ?/?/??

2 Objectives What is a mineral? Define a mineral.
Describe how minerals form. Identify the most common elements in Earth’s crust. Potash Liroconite Gold Sphalerite

3 Minerals Minerals always exist in a solid(1) form. Salt

4 Minerals (continued) A naturally occurring(2) substance is one that is made by natural processes. Thus, a substance developed in a lab, such as a synthetic diamond, cannot be considered a mineral. An inorganic substance is one that is not alive nor has ever been alive. Therefore coal, formed by an organic process, is not a mineral.

5 Minerals - composition
Although a few minerals are composed of single elements, most are made from compounds. (Mg,Fe)2SiO4 SiO2 Olivine Quartz Solids with a specific chemical composition.(3)

6 Mineral - crystals Crystal – Solid in which the atoms are arranged in repeating patterns(4)

7 Mineral – crystals (continued)
A mineral can take the shape of one of the six major crystal systems.

8 Magma Magma - Molten material found beneath Earth’s crust.

9 Minerals - formation Minerals can form when differences in density force magma upward into cooler layers of Earth’s interior.

10 Minerals - magma When compounds in cooling magma no longer move freely, they may interact chemically to form minerals.

11 Minerals – formation (continued)
Mineral crystals may begin to precipitate out of a solution that has become saturated. Always have a scale in science images

12 Minerals – formation (continued)
Minerals form from cooled magma and from elements in solutions.

13 Earth’s Crust – abundant elements
The most abundant elements in Earth’s crust are silicon and oxygen.

14 Silicates Silicate - Mineral that contains silicon and oxygen. These make up the most common mineral group. Silicates Sub-classification based on tetrahedral structure Non-Silicates Natives elements – only one element Sulfides - with a sulfur; tellurium, arsenic, or selenium Oxides – O22- Halides - (fluorine, chlorine, iodine, and bromine) is the main anion. Carbonates – [CO3]2- Sulfates – [SO4]2- Phosphates – [PO4]3-

15 Common Minerals The most common minerals, feldspar and quartz, are silicates.

16 Think about it If you took random samples of minerals from several locations, which type of mineral would you likely have more of—oxides, silicates, or carbonates. Why? There likely would be more silicates than other types because 96 percent of the minerals in Earth’s crust are silicates.

17 Known Minerals There are at least 4,900 known minerals in Earth’s crust.

18 Ore Minerals that contains a useful substance that can be mined for profit. Peacock Ore - copper Argentite - silver

19 Ore - continued The classification of a mineral as an ore may change once it has been mined.

20 Ore - continued Ores near Earth’s surface generally are obtained from open-pit mines. “525 m deep, 1200 meters in diameter. The air zone within this mine is closed for helicopters - a few accidents occurred when they were “sucked in” by downward air flow…”

21 Gem Valuable mineral prized for its rarity and beauty

22 Remember there was a reason for taking those class notes . . .
Quiz Break Remember there was a reason for taking those class notes . . . Quiz Break

23 Of Identifying minerals
Objectives Of Identifying minerals Classify minerals according to their physical and chemical properties. Identify different types of minerals. Discuss how minerals are used. Potash Liroconite Gold Sphalerite

24 ID-ing Minerals Minerals can be identified based on their physical and chemical properties. Physical Chemical

25 ID-ing Minerals - luster
Silver, gold, and copper have shiny surfaces and thus are said to have metallic luster. Luster is described as either metallic or nonmetallic. Gold Silver Copper

26 ID-ing Minerals - streak
A mineral’s streak rarely changes, but sometimes does not match its external color, even if it is weathered or its external color varies slightly.

27 ID-ing Minerals – trace elements
Trace elements in a mineral can affect the color or the value of mineral.

28 ID-ing Minerals – luster & streak
Luster is the way a mineral reflects light from its surface, while streak is the color of a mineral when it is broken up and powdered. Both are tests used to identify a mineral.

29 ID-ing Minerals – specific gravity
Geologists commonly use specific gravity as a measure of density for accurate identification of a mineral.

30 ID-ing Minerals – density vs. specific gravity
Density is the ratio of the mass of a substance divided by its volume. Specific gravity is the most common measure of density. It is the ratio of the weight of a substance to the weight of an equal volume of water.

31 ID-ing Minerals - hardness
Mohs scale is used to compare the hardness of minerals. Finger nail ~2.2 Glass, steel knife ~ 5.5 Streak plate 7

32 ID-ing Minerals - cleavage
Mica has perfect cleavage in one direction; it breaks in sheets.

33 ID-ing Minerals - fracture
When flint and opals break, they have a unique fracture with arclike patterns.

34 ID-ing Minerals – cleavage & fracture
Minerals with cleavage split easily and evenly along one or more planes, while minerals with fracture break unevenly along jagged edges. Both describe how minerals split due to their atomic arrangements.

35 ID-ing Minerals – hardness & texture
Hardness is a measure of how easily a mineral can be scratched, while texture describes how a mineral feels. Both are tests used to identify a mineral.

36 ID-ing Minerals - inorganic
A mineral, such as salt, is naturally occurring but inorganic, in contrast to sugar, which comes from plants.

37 The most reliable way to identify a mineral is by using a combination of several tests.
cleavage - Property of splitting along one or more flat planes evenly and easily fracture - Property of breaking with rough or jagged edges hardness - Measure of how easily a mineral can be scratched streak - Color of a mineral when it is broken up and powdered luster - The way a mineral reflects light from its surface

38 Why do geologists usually use a combination of tests to identify a mineral?
Some minerals have characteristics similar to other minerals. Therefore, more than one test may be necessary to accurately identify the minerals.

39 ID-ing Minerals – specific gravity
Chemical Formula Breakage Pattern Gold 19.3 Au Hackly Apatite 5 Ca5(PO4)3(F, OH, Cl) Uneven fracture Pyrite 5.2 FeS2 Garnet 3.5–4.3 (Mg, Fe, Ca) 3 (Al2Si3O12) Conchoidal fracture Beryl 2.75 Be3Al2Si6O18 Corundum 4 Al2O3 Fracture If the volume of the sample of beryl equals the volume of the sample of gold, how many times greater is the mass of the gold sample than the mass of the beryl sample? SG 19.3 ÷ 2.75 = 7.02 times greater

40 ID-ing Minerals - Hardness
Color Hardness Gold Metallic gold 2.5–3 Apatite Blue, green 5 Pyrite Metallic pale brass, gold 6–6.5 Garnet Red, deep red, brown 6.5–7.5 Beryl Bluish green, green 7.5–8 Corundum Red, deep red 9

41 ID-ing Minerals - Hardness
Color Hardness Gold Metallic gold 2.5–3 Apatite Blue, green 5 Pyrite Metallic pale brass, gold 6–6.5 Garnet Red, deep red, brown 6.5–7.5 Beryl Bluish green, green 7.5–8 Corundum Red, deep red 9 Which mineral can scratch at least one of the green stones? Which mineral can scratch neither green stone? Which mineral can scratch at least one of the red stones? Which mineral can scratch neither red stone? Which mineral can scratch only one of the green stones? pyrite gold beryl apatite garnet

42 Remember there was a reason for taking those class notes . . .
Quiz Break 2 Remember there was a reason for taking those class notes . . . Quiz Break


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