4.1 Minerals

1. 4.1 Minerals The Earth’s crust is composed of about 3000 minerals. Minerals are naturally occurring, inorganic solids with a specific composition and definite crystal structure.

2. What does this definition encompass? • naturally occurring – not a synthetic diamond • Inorganic (No Carbon) – not sugar or coal • Specific composition – this can be a range of compositions • Ex: Olivine contains Fe, Mg and Si. Rocks are considered Olivine so long as the ratio of Mg + Fe remains constant Si

3. Olivine types -often found in igneous rocks • Peridot is a semiprecious stone • non transparent olivine

4. Definite Crystalline structure – there are 6 crystal systems

5. Cubic Crystals – 6 equal sides • Ex Diamond • Fluorite CaF2

6. Tetragonal – elongated cube • Wulfenite PbMoO4 • Cassiterite SnO2

7. Orthorhombic – elongated rectangle • Topaz Al2SiO4(F,OH)2 • Natrolite Na2Al2Si3O10-2H2O

8. Monoclinic – tetragonal pushed sideways • Gypsum CaSO4•2(H2O) • Nissonite Cu2Mg2(PO4)2(OH)2 · 5H2O

9. Triclinic – orthorhombic pushed sideways • Feldspar KAlS3O8 - NaAlSi3O8 - CaAl2SSi2O8 • Bluestone CuSO2•5H2O

10. Hexagonal – elongated hexagon • Pyromorphite Pb5(PO4)3Cl • Aquamarine Be3Al2Si6O18

11. Sources of Minerals • Magma – as it cools, the components interact to form minerals • Large crystals form if the magma cools slowly • The type of mineral formed depends on the ingredients of the magma • Solution – A supersaturated solution or a solution from which the water evapourates will have minerals crystallize out

12. Mineral Groups in the Earth’s Crust • There are 30 common minerals 1. Silicates – 96% of crust minerals ex feldspar and quartz - Form a tetrahedron

13. Arrangements for Tetrahedrae A. Chains B. Double Chains

14. C. Tetrahedral sheets

15. Mica is an example of a tetrahedral sheet where Al or K bond the successive sheets together, but these bonds are very weak so the crystal cleave along the sheets. USES: Oven Glass

16. 2. Carbonates CO3 which is bonded to one or two metal ions • Gemstones include Malachite and azurite • Rocks include limestone, dolomite and Marble

17. 3. Oxides are composed of a metal ion plus oxygen • Iron Oxides like hematite and magnetite • Uranium Oxides like uranite (used as nuclear fuel)

18. 4. Sulfides are compounds containing sulfur and other compounds • Pyrite (FeS2 or fools gold)

19. 5 Sulfates are compounds containing SO4 • CaSO4 (Gypsum)

20. 6 Halides composed of a halogen and a metal • Sylvite

21. 7. Native Elements which are solid and relatively pure forms of metals Ag, Au and Cu • Native Silver • Native Gold

22. Hwk # 1,2,6,7 p 83