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Oxides and Hydroxides

Oxides and Hydroxides . GLY 4200 Lab 3 - Fall, 2012. Oxides. Oxygen is by far the most abundant element in the earth’s crust > 60% by atomic proportion Many minerals contain oxygen Only those minerals where the oxygen is combined with metallic elements directly are oxides .

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Oxides and Hydroxides

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  1. Oxides and Hydroxides GLY 4200 Lab 3 - Fall, 2012

  2. Oxides • Oxygen is by far the most abundant element in the earth’s crust • > 60% by atomic proportion • Many minerals contain oxygen • Only those minerals where the oxygen is combined with metallic elements directly are oxides

  3. Anionic Groups Containing Oxygen • Almost all non-metallic elements form structural groups with oxygen, and then these groups combine with the metallic elements • Examples: • Carbonates CO3 • Phosphates PO4 • Tungstates WO4

  4. Oxide Classification • Oxides can be divided into classes • Simple oxides, which contain one cation type in association with oxygen • Multiple oxides, which contain more than one cation type in association with oxygen • Hydroxides are minerals which contain the OH-1 group, the oxygen’s are directly bound to the metal with a single bond

  5. Simple Oxides • Possible types: XO, X2O, XO2, X2O3 • X is a metal cation

  6. Multiple Oxides • Possible types: XY2O4, and XY2O6 • X and Y are metal cations

  7. Oxide Group Properties • Dense • Relatively hard • Refractory (melt at a high temperature) • Occurance: • Often found as accessory minerals in igneous and metamorphic rocks • Because of their hardness, as resistant grains and detrital grains in sediments and sedimentary rocks

  8. Hydroxide Group Properties • Usually soft to moderate hardness • Lower densities than oxides • Occurance: alteration products formed by weathering, hydroxides are necessarily low-temperature minerals • High temperatures would cause dehydration and would destroy the crystal structure

  9. Ore Minerals • It is harder to obtain metals from oxides than from sulfides, because metal-oxygen bonds are stronger • Some elements prefer to bond to oxygen, and do not occur as sulfides, so the ores are oxides

  10. Oxide Ores

  11. Hydroxide Ore • Bauxite is the major ore of aluminum • It is a rock name, not a mineral name • Mixture of diaspore, gibbsite, and boehmite

  12. Text Reference • See chapter 16 in the text for more information on oxides and hydroxides, pp. 368-393

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