MINERAL CVE2204+Week+5+Notes+and+answers.pdf
- 1. CVE 2204 Engineering Geology Minerals CLO2: Describe the formation and the characteristics of the various types of soils and rocks
- 2. Rock Mass
- 3. Introduction • Rocks itself is both construction materials or part of engineering structure (cut slope, foundation, tunnel) • Rocks are in 3 types – igneous, sedimentary, metamorphic • Rocks: solid mass of mineral that occurs naturally as part of our planet
- 4. Minerals • Almost every manufactured product contains minerals. They are essential for the development of a modern society • Rocks are Earth materials made from minerals • All geological processes on earth such as volcanic eruption, earthquake, landslide, and erosion involve earth materials (and minerals are the building blocks of earth materials) • Basic knowledge of earth materials is essential to the understanding of all geological phenomena
- 5. The big picture Elements combine to form the natural compounds Atoms make up elements Natural compounds and elements combine to form minerals. Minerals make up rocks. Rocks make up the Earth. pure chemical substance made of one type of atom (eg. O2, H2) Different elements combined together in a fixed ratio (eg. H2O)
- 6. Minerals: Building blocks of rocks • Geological definition of a mineral: • Naturally occurring • Inorganic • Solid • Ordered internal molecular structure • Definite chemical composition • Rocks – consist of one or more minerals • Eg. Mineral: calcite; rock: limestone • > 3500 elements identified, only 8 most common elements forming mineral
- 7. Element in Earth’s Crust Element Symbol % of earth’s crust Oxygen O 49.52 Silicon Si 25.75 Aluminium Al 7.51 Iron Fe 4.70 Calcium Ca 3.39 Sodium Na 2.64 Potassium K 2.40 Magnesium Mg 1.94 Total % 97.85 % of other elements 2.15 pure chemical substance made of one type of atom (eg. O2, H2)
- 8. Example of Minerals Pink chalcedony Sulphur Azurite Fluorite
- 9. Minerals • Minerals – naturally occurring inorganic solids, which possess a definite internal structure and specific chemical composition • Gold is mineral? • Synthetic diamonds are minerals? • Petroleum is mineral? • Animal bone is mineral? • Steel is mineral?
- 10. Mineral Group • Basically silicate and non-silicate (carbonate) mineral groups • Minerals containing silica = silicates minerals (Olivine Mg2Fe2SiO4 & Orthoclase KAlSi3O8). • Silicon + oxygen = silica (Quartz SiO2 is pure silica) • 2 subgroups of silicate mineral: • Ferromagnesian silicates: (dark colour, > dense). • Non-ferromagnesian silicates : (light colour, < dense) • Carbonate mineral (non-silicate) : • minerals calcite (CaCO3) : limestone • mineral dolomite CaMg(CO3)2: dolostone
- 11. Mineral Group
- 12. How are Minerals Identified? • By different properties (physical, mechanical, chemical) • Colour • Cleavage • Lustre • Hardness • Specific gravity • Others
- 13. Colour • Generally an unreliable diagnostic property to use for mineral identification • Often highly variable for a given mineral due to slight changes in mineral chemistry • Impurities of quartz give variety of colour (pink, purple, milky white) Same minerals existed in different colours
- 14. Cleavage • In crystalline structure, some bonds are weaker than others • Cleavage is the tendency of minerals to break along planes of weak bonding • Normally, produces flat, shiny surfaces • Fracture (mineralogy): tendency of a mineral to break without a definite shape (mineral not exhibit cleavage)
- 16. Cleavage (directions @ angles)
- 18. Fracture Comparison of fibrous fracture and conchoidal fracture. Conchoidal fracture Fibrous fracture
- 19. Lustre • Lustre – the appearance of light reflected from the surface of a mineral • Metallic lustre – minerals that have appearance in metals • Nonmetallic lustre – glassy, dull silky The freshly broken sample of galena displays a metallic lustre, whereas the sample on the left is tarnished and has a submetallic lustre.
- 20. Hardness • Measure of the resistance of a mineral to abrasion or stretching • Determine by rubbing the mineral to identified against another mineral of known hardness • Measured on a qualitative scale called Moh's Hardness Scale. • Examples: Fingernail = 2.5, Glass = 5.5, Streak Plate = 6.5, Talc =1, Quartz = 7, Diamond = 10.
- 21. Hardness
- 22. Specific gravity • Ratio of the weight of a mineral to the weight of an equal volume of water • Eg. 1cm³ of mineral weights 3 times as much as 1cm³ of water; SG = 3.0 • Average value is approximately 2.7 • SG of pure 24 karat gold = 20
- 23. Others • Magnetism (magnetite) • Reaction to HCl (carbonate) • Double refraction (calcite) • Taste (halite) • Smell (sulphur) • Elasticity (mica) • Malleability (gold)