Minerals

1. Minerals Chapter 2

2. Mineral: a naturally occurring substance formed in the Earth • Inorganic • Solid substance • Definite chemical composition

3. How Minerals Form 1. Crystallization from magma 2. Precipitation 3.Pressure and temperature 4. Hydrothermal solutions

4. Mineral Groups • Can be classified based on their composition 1. Silicates • Silicon and oxygen combine to form a structure called the silicon-oxygen tetrahedron. 2. Carbonates • Minerals that contain the elements carbon, oxygen, and one or more other metallic elements 3. Oxides • Minerals that contain oxygen and one or more other elements, which are usually metals

5. Mineral Groups 4. Sulfates and Sulfides • Minerals that contain the element sulfur 5. Halides • Minerals that contain a halogen ion plus one or more other elements 6. Native elements • Minerals that exist in relatively pure form

6. Over 2,000 are known!

7. Identifying Minerals: 1. Color • Most easily observed property • Yet, least useful property

8. Identifying Minerals:ColorWhy it is the least useful property… • Different minerals have the same color • One mineral can have different colors • Impurities can alter color • Some change color when exposed to air • Light can distort color

9. Identifying Minerals: 2. Luster • Way a mineral shines

10. Identifying Minerals: Luster Metallic: shines like polished metal Pyrite “Fool’s Gold”

11. Identifying Minerals: Luster Nonmetallic: does not shine like metal

12. Identifying Minerals: Luster Pearly like a pearl Talc

13. Identifying Minerals: Luster Greasy Turquoise

14. Identifying Minerals: Luster Vitreous like shining glass Amethyst

15. Identifying Minerals: Luster Resinous like wax

16. Identifying Minerals: Luster Dull or Earthy Bauxite

17. Identifying Minerals: 3. Crystal Shape • The shape of a crystal results from the way the atoms of a mineral come together as the mineral forms

18. Identifying Minerals: 4. Streak Test • Color of a mineral’s powder form • Usually, streak is not the same color as the mineral • Streak doesn’t vary

19. Identifying Minerals: Streak Test • Metallic mineral has dark streak • Nonmetallic – colorless or light streak

22. Identifying Minerals: 5. Cleavage • The splitting of a mineral along certain flat surfaces • Related to the types of bonds in the internal structure of the mineral

23. Identifying Minerals: Cleavage

24. Mica Has Cleavage in One Direction

25. Identifying Minerals: 6. Fracture • the way a mineral tends to break –unevenly!!!

26. Identifying Minerals: Fracture Splintery jagged

27. Identifying Minerals: 7. Hardness • Resistance to being scratched • Moh’s hardness scale

28. Mohs Scale, identified numerically by standard minerals, from 1 (softest) to 10 (hardest): 1. Talc 2. Gypsum 3. Calcite 4. Fluorite 5. Apatite 6. Orthoclase 7. Quartz 8. Topaz 9. Corundum 10. Diamond

30. To remember the Mohs scale try remembering this phrase: The Geologist Can Find An Ordinary Quartz, (that) TouristsCall Diamond!

31. Tools for Testing Hardness • You typically do not carry around a supply of the 10 minerals on the hardness scale. However, you can use the following items to help estimate the hardness of a mineral:

32. Tools for Testing Hardness • finger nail (H = 2.5) • penny (H = 3.5) • common nail (H = 4.5) • glass plate (H = 5.5)

33. Identifying Minerals: Special Properties • Acid test http://www.westhamptonbeach.k12.ny.us/Teachers/Cohen/sciweb/earthscience/sedimentary/Mvc-327w.mpg

34. Identifying Minerals: Special Properties • Magnetic test

35. Identifying Minerals: Special Properties • Taste test Some minerals have a distinct taste. Never do this test after the acid test!

36. Common Rock-forming Minerals Quartz

37. Feldspar Mica

38. Talc Amphiboles

39. Galena Halite

40. Biotite Calcite

41. Hematite Pyrite

42. Magnitie Olivine

43. Garnets