Major Mineral Groups: Silicates, Carbonates, Oxides, and Sulfides

1. Mineral Groups Chapter 5.4

2. Major Mineral Groups Silicates Carbonates Oxides and Sulfides

3. I Silicate Group • 90% of all minerals fall within this group • Silicon and oxygen compound with some type of metallic element • Forms a silica tetrahedron = 4 oxygen bound to 1 silicon atom • Are classified according to the way that the tetrahedra are linked together

4. Silicate Families • Feldspar • Quartz • Pyroxene • Mica

5. 1. Feldspar • Most abundant family of minerals • Makes up 60% of Earth crust • All feldspars share three features • Two directions of cleavage • Hardness of 6 • Pearly luster

6. 2 Major Groups • Feldspars are classified into two major groups • Potassium Feldspars • Sodium-calcium Feldspars

7. Potassium Feldspar • The most common potassium feldspar is orthoclase • Light colored – pink or salmon • Two cleavage surfaces meet at right angles • Commonly found granite

8. Sodium-Calcium Feldspar • Called Plagioclase Feldspar • Color ranges from white to gray • Two cleavages surface at slightly less than a right angle • One cleavage surface is marked by fine parallel lines – called striations

9. Feldspar Uses Rock-forming minerals Used in the manufacturing of glass and ceramics

10. 2. Quartz Second most abundant mineral Chemical formula SiO2 Made entirely of tightly bound silica tetrahedra

11. Luster & Color • Glassy or greasy luster • Pure quartz is colorless • colored varieties include: rose quartz, amethyst, and smoky quartz

12. Fracture & Hardness • Conchoidal or irregular fracture • Hardness of 7 • Hardest common mineral

13. Quartz Uses • The hardness and optical properties of quartz makes it ideal for certain industrial uses • Watch movements, prisms, heat lamps, lenses, glass, and paints • Semiprecious gemstone – often worn as jewelry

14. 3. Pyroxene • Occur widely • Cleavage surfaces meet nearly at right angles • Example: Augite • Most common • Dark in color • Ferromagnesian silicate – contains iron and magnesium

15. 4. Mica • Soft silicates • Harness of 2.5 • Perfect cleavage • Form flat crystals that cleave in only one direction to form thin sheets or flakes • Muscovite – silvery white • Biotite – brown or black

16. Mica Uses • Useful in both sheets and powders • Electronic insulators • Paints • Plastics • Rubber • Roofing

17. Other Silicates Amphibole Minerals • Form long, needlelike crystals • Hornblende - most common • Shiny dark green, brow, or black • Hardness of 5 to 6 • Found in igneous and metamorphic rock

18. II Carbonates • Made of negatively charged carbonate ions bonded to positive metal ions • Each carbonate ion is made of one Carbon atom covalently bonded to three oxygen atoms • Examples: • Calcite • Dolomite

19. Carbonate Uses • The rocks limestone and marble consist almost entirely of carbonate minerals • Used in construction • Limestone is also used in a variety of everyday products including paper and medicine

20. Calcite The most common carbonate mineral Colorless or white Hardness of 3 – can be scratched with a knife Three perfect cleavages Can use an acid test to identify calcite

21. Dolomite Hardness of 3.5 to 4 Cleaves into rhombohedra Does not bubble with hydrochloric acid Appears as coarse or fine grains in dolomitic limestone

22. III Oxides and Sulfides • Minerals that have significant amounts of the element iron • Oxide – mineral consisting of a metal element combined with oxygen • Sulfide – mineral consisting of a metal element combined with sulfur

23. Oxide and Sulfide Uses • Used to Make • Steel • Magnets • Car parts • Medicines • Cosmetics • Plastics • Paints

24. Hematite Most common iron oxide Red Earthy lust Uneven fracture Red-brown streak Hardness 5-6

25. Magnetite Black iron oxide Attracted to magnets Hardness between 5.5 to 6.5

26. Pyrite Most common iron sulfide mineral Color ranges from pale brass to golden yellow Harness of 6 6 – 12 sided crystal Also called fool’s gold