Transcript Slide 1
Physical Science Rocks and Minerals Rocks Igneous rocks – • Formed by the cooling and crystallization of hot molten rock called magma • Igneous means – formed by fire • 95% of the earth crust are igneous rocks • examples include basalt and granite From yahoo images Rocks Sedimentary rocks – From yahoo images • Formed by weatherd material carried by water, wind or ice. • Most common rock in the upper part of the earth’s crust • They cover 2/3 of earths surface. • Examples include sandstone, shale and limestone Rocks Metamorphic rocks – • Formed from pre-existing rocks that are transformed under high • temperature and pressure. • Metamorphic means – changed in form • Examples include marble, slate and diamond From yahoo images Minerals • • • Minerals – The building blocks of rocks. Minerals are naturally formed, generally inorganic crystalline solid composed of an ordered array of atoms having a specific composition. Minerals differ from one another in their combination and proportion of elements and internal arrangement of atoms. Classifying Minerals • Crystal form – shape of crystal structure. Classifying Minerals • Crystal form – shape of crystal structure. Classifying Minerals • Polymorph – mineral composed of the same atom but have different crystal structure. Classifying Minerals Mohs Hardness Scale Hardness is measured on the Mohs Scale, identified numerically hardness of by standard minerals, from 1 (softest) to 10 (hardest): 1. Talc 2. Gypsum 3. Clacite 4. Fluorite 5. Apatite 6. Orthoclase 7. Quartz 8. Topaz 9. Corundum 10.Diamond • A mineral of a given hardenss will scratch a mineral of a lower number. With a systematic approach, you can use minerals of known hardness to determine the relative hardness of any other mineral. Classifying Minerals • Cleavage – tendency of a mineral to break along planes of weakness. • Fracture – break that is not along the lines of a cleavage plane From yahoo images Classifying Minerals • Luster – appearance of its surface as it reflects light • Luster is independent of color From yahoo images Classifying Luster of Minerals • • • • • • • • • • • • • • Adamantine - very gemmy crystals Dull - just a non-reflective surface of any kind Earthy - the look of dirt or dried mud Fibrous - the look of fibers Greasy - the look of grease Gumdrop - the look a sucked on hard candy Metallic - the look of metals Pearly - the look of a pearl Pitchy - the look of tar Resinous - the look of resins such as dried glue or chewing gum Silky - the look of silk, similar to fibrous but more compact Submetallic - a poor metallic luster, opaque but reflecting little light Vitreous - the most common luster, it simply means the look of glass Waxy - the look of wax Classifying Minerals • Color – is usually a poor way to judge minerals – the same mineral may exhibit a variety of colors • Streak – color or mineral in its powder form. Usually obtained by rubbing across a porcelain plate. From yahoo images Classifying Minerals • Specific Gravity – Density like measurement based on a comparison with the density of water. From yahoo images Classifying Minerals • Chemical properties – fiz test – add HCl to carbonates and it will fizz Makeup of Rocks and Minerals • • • • • 118 know elements 88 are naturally occurring These combine to make 3400 different minerals About two dozen minerals are abundant These are made from 8 elements Makeup of Rocks and Minerals Makeup of Rocks and Minerals • • • These 8 elements make up 98 % of the mass of the crust Half of this mass is due to O alone These minerals are broken into groups – silicates oxides & carbonates sulfides & sulfates Building blocks of rock forming minerals • Silicates – silicon with oxygen – SiO4 Building blocks of rock forming minerals • Silicates – silicon with oxygen – SiO4 Oxides and Carbonates • Oxides – metals combined with oxygen Iron (hematite-magnetite) chromium (chromitite) manganese (pyrolusite) tin (cassiterite) uraninum (uraninite) Hemetite From yahoo images • Most metals come from these ores Oxides and Carbonates • Carbonates – minerals composed of carbonate ion CO3 Calcite – calcium carbonate CaCO3 Dolomite – calcium and magnesium carbonate CaMg(CO3)2 These two make up limestone calcite From yahoo images Sulfides and Sulfates minerals composed of sulfur S and Sulfate SO42- • Pyrite – fools gold FeS2 • Gypsum – calcium sulfate CaSO4 pyrite From yahoo images