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Minerals.

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Presentation on theme: "Minerals."— Presentation transcript:

1 Minerals

2 Minerals Natural, usually inorganic solid that has a characteristic chemical composition, an orderly internal structure, and a characteristic set of physical properties.

3 Is it a Mineral? Is it organic? Does it occur naturally?
Is it a crystalline solid? Consistent chemical composition? Must answer yes to all 4 questions for it to be a mineral

4 10 Most common minerals Quartz Calcite Orthoclase Dolomite
Plagioclase Halite Muscovite Gypsum Biotite Ferromagnesian Calcite Minerals These make up 90% of Earth’s mass

5 Mineral Groups Silicates 96% of Earth’s crust Contains Si and O
Can have other elements also Feldspar – Orthoclase if K, Plagioclase if Na or Ca Ferromagnesian minerals – rich in Fe

6 Mineral Groups Nonsilicate Minerals Do not contain Si and O Six groups
Can contain one or the other, but not both Six groups Carbonates Native elements Halides Oxides Sulfates Sulfides

7 Crystalline Structure
Crystal – atoms, ions, or molecules are arranged in a regular, repeating pattern Silicate crystal structure Silicon – oxygen tetrahedron 1 Si with 4 O’s around it Basic building block of silicates Can be connected 6 different ways

8 Crystalline Structure
Nonsilicate crystals Diverse chemical composition leads to variety of crystal structures Cubes, hexagonal prisms… Crystal structure influences physical properties Native elements are dense due to compact crystal structure

9 Silicate Tetrahedron

10 Physical Properties of Minerals
Mineralogist Examine, analyze, and classify minerals Result from chemical composition and crystal structure Can be useful in identifying minerals

11 Physical Properties Color Not reliable for ID purposes
Small amount of impurities can affect color Weathered surfaces may hide color Only look at fresh surfaces

12 Color

13 Physical Properties Streak Color of mineral in powder form
Streak plate – unglazed ceramic tile Streak color may differ from mineral color Metallic minerals – darker streak Nonmetallic minerals – lighter streak

14 Streak

15 Physical Properties Luster Light reflected from mineral’s surface
Metallic luster – shiny surface Nonmetallic luster Glassy Waxy Pearly Brilliant Dull / Earthy

16 Metallic Luster

17 Glassy Luster Quartz

18 Waxy Luster Variscite

19 Pearly Luster Talc

20 Brilliant Luster Diamond

21 Dull / Earthy Luster Psilomelane

22 Physical Properties Cleavage / Fracture Cleavage Fracture
splitting along specific lines of weakness Forms smooth, flat surfaces Fracture Break unevenly into pieces Forms curved, irregular surfaces Conchoidal fractures – curved surface

23 Cleavage - Calcite

24 Fracture Conchoidal

25 Fracture Irregular

26 Physical Properties Hardness Ability to resist scratching
Mohs Hardness Scale Scale of 1 to 10 1 = Talc 10 = Diamond Glass is about a 5

27 Mohs Hardness Scale

28 Physical Properties Crystal Shape Density 6 Basic shapes
Certain minerals always form crystals with the same shape Density Ratio of mass to volume Can help identify minerals

29 Crystal Shapes

30 Physical Properties Fluorescence and phosphorescence
Chatoyancy and asterism Double refraction Magnetism Radioactivity

31 Double Refraction


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