Introduction to Minerals

1. Introduction to Minerals Definition, Classification, Identification

2. Introduction to Minerals:Outline • Criteria to “qualify” as a mineral • Formation of minerals (in brief) • Classification of minerals • Identification of minerals

3. Definition of a Mineral • Five Criteria: • Solid • Naturally Occurring • Inorganic • Definite Chemical Composition • Crystal (adj: Crystalline)

4. Definition of a Mineral:Naturally Occurring http://en.wikipedia.org/wiki/File:Glass-Ball.jpg

5. Definition of a Mineral:Inorganic http://en.wikipedia.org/wiki/File:Kandiszucker_wei%C3%9F.jpg

6. Definition of a Mineral:Definite Chemical Composition • Example: • “Halite” just is NaCl • There may be slight impurities. http://en.wikipedia.org/wiki/File:Selpologne.jpg

7. Definition of a Mineral:Crystal Structure • Atoms form an orderly and repeating arrangement • Atoms form an orderly and repeating arrangement • Atoms form an orderly and repeating arrangement • Atoms form an orderly and repeating arrangement • Atoms form an orderly and repeating arrangement • Atoms form an orderly and repeating arrangement http://en.wikipedia.org/wiki/File:Halite-249324.jpg

8. Formation of Minerals • Must have conditions for good crystal growth! • One: Slow cooling of “magma” – hot, liquid rock material • Two: Slow evaporation of water that has dissolved compounds • Forms an “evaporite” (see next slide)

9. Formation of Minerals:Evaporite Example http://en.wikipedia.org/wiki/File:HaliteEncrustedCobbleDeadSea.JPG

10. Classification of Minerals • Classified based on CHEMICAL COMPOSITION • i.e., what they’re made of • there is tolerance or “fudge factor” for some small impurities • The following are MAJOR groups, but not exhaustive!

11. Classification of Minerals:Silicates • Silicates contain silicon and oxygen in the chemical formula • Example: Quartz, SiO2 (the simplest example) http://en.wikipedia.org/wiki/File:QuartzUSGOV.jpg

12. Classification of Minerals:Oxides • Oxides contain oxygen in the chemical formula (except when part of another class) • Example: Hematite, Fe2O3 http://en.wikipedia.org/wiki/File:Hematite.bear.660pix.jpg

13. Classification of Minerals:Sulfides • Sulfides contain sulfur in the chemical formula (except when part of another class) • Example: Pyrite, FeS2 http://en.wikipedia.org/wiki/File:2780M-pyrite1.jpg

14. Classification of Minerals:Halides • Halides contain a halogen (Group 17 element) in the chemical formula • Example: Fluorite, CaF2 http://en.wikipedia.org/wiki/File:Fluorite_crystals_%28Cullen_Hall_of_Gems_and_Minerals%29.jpg

15. Classification of Minerals:Carbonates • Carbonates contain the polyatomic ion “carbonate” in the chemical formula • i.e., CO3 (which has a 2- charge) • Example: Calcite, CaCO3 • Note that this is NOT an oxide. http://en.wikipedia.org/wiki/File:Calcite_jaune.jpg

16. Classification of Minerals:Sulfates • Sulfates contain the polyatomic ion “sulfate” in the chemical formula • i.e., SO4 (which has a 2- charge) • Example: Celestite, SrSO4 • Note that this is NOT an oxide NOR a sulfide. http://en.wikipedia.org/wiki/File:Celestitemadagascar.jpg

17. Identification of Minerals • Guiding Principles • A single test is never good enough. • Many minerals STRONGLY RESEMBLE other ones. • Even individual samples can be outside the norm.

18. ID of Minerals:Color Test http://en.wikipedia.org/wiki/File:Citrin_cut.jpg http://en.wikipedia.org/wiki/File:QuartzUSGOV.jpg http://en.wikipedia.org/wiki/File:Ele.rose.750pix.jpg http://en.wikipedia.org/wiki/File:Amethyst._Magaliesburg,_South_Africa.jpg http://en.wikipedia.org/wiki/File:Quarzo_morione.jpg http://en.wikipedia.org/wiki/File:Green_quartz.jpg

19. ID of Minerals:Luster • Metallic vs. • Nonmetallic • glassy, vitreous, dull, etc. http://en.wikipedia.org/wiki/File:2780M-pyrite1.jpg http://en.wikipedia.org/wiki/File:Citrin_cut.jpg

20. ID of Minerals:Scratch Test (Hardness) • Mohs Scale of Hardness • “To scratch, or to be scratched?” • System is just relative rankings (“ordinal”) http://geology.csupomona.edu/mineral/mohs.gif

21. ID of Minerals:Streak Test http://en.wikipedia.org/wiki/File:Streak_plate_with_Pyrite_and_Rhodochrosite.jpg

22. ID of Minerals:Crystal Shape http://en.wikipedia.org/wiki/File:2780M-pyrite1.jpg http://en.wikipedia.org/wiki/File:Halite-249324.jpg

23. ID of Minerals:Breaking Good? • CLEAVAGE • Some minerals break along a flat plane, forming a smooth surface • E.g., “basal cleavage” is breaking into thin sheets http://en.wikipedia.org/wiki/File:Fluorita_green.jpeg

24. ID of Minerals:Breaking Bad?! • FRACTURE • Other minerals break in jagged or curved ways “conchoidal fracture” - forms smooth, rounded edges http://en.wikipedia.org/wiki/File:Green_quartz.jpg http://en.wikipedia.org/wiki/File:Lipari-Obsidienne_%285%29.jpg

25. ID of Minerals:Miscellaneous Tests • Taste test?! (DO NOT DO THIS ONE.) • Magnetism test • UV light test (at bottom left) • Optical test (for calcite only, at bottom right) • Carbonate / acid test (see next slide) http://en.wikipedia.org/wiki/File:Crystal_on_graph_paper.jpg http://en.wikipedia.org/wiki/File:FluoriteUV.jpg

26. ID of Minerals:Carbonate / Acid Test • Any carbonate mineral should react with hydrochloric acid: XCO3 + 2HCl → XCl2 + H2O + CO2

27. Check Yourself • Attempt to classify these minerals: • Molybdenite, MoS2 • Kyanite, Al2SiO5 • Blodite, Na2Mg(SO4)2 • Why is color not a good indicator of a mineral’s identity? • What kinds of conditions form good mineral samples?

28. MINERALS