GEOS1211 Lecture Notes - Lecture 5: Orthoclase, Augite, Hornblende
14 Jun 2018
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Lecture 5 learning outcomes
• Define what is a mineral
- Naturally occurring
- Inorganic
- Homogenous solid
- Fairly definite chemical composition
- Ordered atomic arrangement (characteristic crystal structure)
• Recognise common minerals
The silica tetrahedra is a basic building block of many minerals
- Olivine (single silicate tetrahedron)
- Pyroxene group (Augite) (single chain silicate)
- Amphibole group (Hornblende) (double chain silicate)
- Micas
o Biotite (sheet silicate)
o Muscovite (sheet silicate)
- Feldspars
o Orthoclase (framework silicate)
o Plagioclase (framework silicate)
Minerals with Iron and magnesium in them are called mafic minerals
Ferromagnesian (dark) silicates (mafic minerals)
- Olivine
- Pyroxene group (augite)
- Amphibole group (hornblende)
- Dark mica (biotite)
Nonferromagnesian (light) silicates (felsic minerals)
- Light mica (muscovite)
- Orthoclase feldspar
- Plagioclase feldspar
- Quartz
Important non-silicate minerals
- Carbonates- calcite and dolomite
- Evaporites- gypsum and halite
- Oxides- magnetite (also goethite and hematite)
• Relate different groups of minerals to typical geological settings and relate changes to
earth/environmental processes
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Document Summary
Lecture 5 learning outcomes: define what is a mineral. Ordered atomic arrangement (characteristic crystal structure: recognise common minerals. The silica tetrahedra is a basic building block of many minerals. Micas: biotite (sheet silicate, muscovite (sheet silicate) Feldspars: orthoclase (framework silicate, plagioclase (framework silicate) Minerals with iron and magnesium in them are called mafic minerals. Oxides- magnetite (also goethite and hematite: relate different groups of minerals to typical geological settings and relate changes to earth/environmental processes. Quartz and the feldspars (framework silicates) are found in a wide range of igneous, sedimentary and metamorphic rock types. In olivine, the si and o are arranged in isolated silica tetrahedra; their negative charges are balanced by. When mg2+ is removed in weathering the mineral structure collapses. Si-o bonds in orthoclase (chains) prevent the framework structure falling apart despite removal of the k+ ions during weathering.
