o FIG. 3.09 * Other mineral groups are much less complicated and much less abundant. o Get chlorides, sulfides, oxides, etc. * Other complex ions such as sulfates (SO 4 ) 4- , carbonates (CO 3 ) 2- , phosphates (PO 4 ) 4- cannot polymerize, hence much simpler (FIG 3.10) * Important minerals: o Calcium carbonate – CaCO 3 – calcite (limestone and marble)
o Calcium sulfate – CaSO 4 – gypsum o Calcium phosphate – apatite * Important diagnostic features – identifying minerals (table 3.4) * Chemistry o Iron most important. Adds color (red/green/brown/black) to minerals when present, raises melting point (along with Mg), and leads to higher density. * Bonding type o Covalent bonded minerals are harder (difficult to break) e And have lower densities. o Ionic bonded minerals as above but in each case less so. e A little easier to break and a little higher density o Van der Waals bonds easily broken, makes minerals soft. * Physical properties used: o Hardness –Moh’s scale (table 3.2) – 1 question on first exam o Cleavage – break open mineral exploiting plane of weak bonding e.g. platy cleavage, breaking mica apart along planes with van der Waals bonding (3.15) o Density – minerals with covalent bonds have lower density. Presence of iorn raises the density of minerals o Crystal form – FIG 3.6 1/30/08 * Other less reliable properties o Color – can be very misleading , minor trace impurities changes color considerably o Luster – appearance in reflected light o Fracture – forceful breaking of mineral o Streak – color of fine powder left on unglazed porcelain sheet (FIG 3.18) * Acid test often useful o FIG 3.14 o Carbonates fizz releasing colorless/odorless gas – carbon dioxide o Sulfides release gas smelling of rotten eggs – H 2 S, SO 2 Solid aggregates of mineral(s) * Look to: o Mineralogy – what minerals it contains; how much of each o Texture – size and shape of mineral crystals and the way they are put together e If crystals visible to naked eye – coarse (grained) e If not visible to naked eye – fine (grained) o Mineralogy and texture tell us how rock was formed * Three rock families:
o Igneous – formed by solidification of molten rock material (magma) – “fire- formed rocks” o Sedimentary – “settled form rocks” o Metamorphic – “changed form rocks” come from existing families (igneous and sedimentary) * IGNEOUS ROCKS: o Two subdivisions: e Intrusive – magma crystallizes deep in crust • Coarse grained crystals • Interlocking crystals e Extrusive – rapidly cooled magma at earth’s surface • Fine grained crystals • Interlocking crystals o Common minerals e Mainly silicates and a few oxides e Table 4.1 o Igneous rocks dominate in the earth’s crust as a whole e About 95% of all rocks in the earth’s crust are igneous rocks * SEDIMENTARY ROCKS: o Formed from sediments – particles formed as preexisting rocks undergo weathering (breakdown) at or near earth’s surface o Sediments are soft, altered by lithification into hard sedimentary rock o The process of lithification involves e Compaction
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