Lecture Note 3 - Physical Geology PDF

7- Hardness (H) - a measure of mineral resistance to scratching. y - A harder substance will scratch a softer one. Mohs Scale of Hardness: w - widely used by geologi...

7- Hardness (H) - a measure of mineral resistance to scratching. y - A harder substance will scratch a softer one. Mohs Scale of Hardness: w - widely used by geologists and engineers. - When identifying a mineral, you should mainly be able to distinguish minerals that are relatively da hard (6.0 or higher on Mohs Scale) from minerals that are relatively soft (less than or equal to 5.5 on Mohs Scale). - You can use common objects such as a glass plate, pocket knife, or steel masonry nail to make Ba this distinction Hard minerals: Will scratch glass; cannot be scratched with a knife blade or masonry nail. Soft minerals: Will not scratch glass; can be scratched with a knife blade or masonry nail. S. an an H r. D Physical Geology Dr. Hanan S. Badawy 8- Tenacity: y - The resistance of a mineral to breakage. w - Some minerals are very hard to break, whereas others are easily broken. Terms used to describe tenacity include brittle (shatters like glass), elastic (like a da plastic comb; bends but returns to its original shape), and malleable (bent permanently into new shapes). - Gold, a soft mineral, is malleable and easily deformed when hit. Ba - Diamond, the hardest known mineral, is very brittle and will shatter when hit. - Do not test the tenacity of mineral specimens unless instructed to do so. S. Other Properties - Reaction to acid - Magnetism an - Specific Gravity (SG) - Feel - Smell an - Taste H r. D  Classification of Minerals Rock-forming minerals: They are the minerals that make up most of Earth’s crust. y Industrial minerals: They are the main non-fuel raw materials used to sustain w industrialized societies. All minerals are also classified into the following chemical classes: da Native minerals are single-element minerals, such as gold, copper, sulphur (sulfur), and graphite. They are elements in pure form, not combined with different elements. Ba Examples include graphite-Diamond C, copper Cu, sulfur S, gold Au, and silver Ag. S. an Hexagonal structure an H r. D  Silicate minerals y - The predominant group in terms of their abundance within the crust and mantle. - Silicates are composed of a combination of SiO4 Tetrahedrons and Cations: K+, w Na+, Ca+2, Mg+2, Fe+2 or Al+3. da - They include the elements silicon and oxygen in varying proportions; - pure silicon dioxide (SiO2) called quartz - silicon-oxygen ions (SiO4)-4 combined with other elements. Examples are olivine: Ba (Fe, Mg)2 SiO4, potassium feldspar: KAlSi3O8 , and kaolinite: Al2 (Si4O10)(OH)8. quartz S. an olivine an H r. D Physical Geology Dr. Hanan S. potassium feldspar Badawy kaolinite  Oxide minerals - contain oxygen (O-2) combined with a metal (except for those containing silicon, y which are silicate minerals). Examples are hematite: Fe2O3, magnetite: Fe2O4 and w corundum: Al2O3. da Ba S. hematite an magnetite Hydroxide minerals an contain hydroxyl ions (OH) - combined with other elements (except for those containing silicon, which are silicate minerals). Examples are goethite: H FeO(OH). r. D goethite