1. Oxides and Hydroxides
GLY 4200
Lab 3 - Fall, 2016

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)
Occurrence:
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
Occurrence: 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 Mineral Element or Gem Cuprite Copper Corundum
Aluminum: Rubies, Sapphires
Hematite, magnetite
Iron
Ilmenite
Titanium
Pyrolusite
Manganese
Cassiterite
Tin
Uraninite
Uranium
Chromite
Chromium
Columbite-Tantalite
Niobium, tantalum

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