Geology Chapter 3 1. Minerals—The Building Blocks of Rocks Define a mineral. A mineral is a naturally occurring, inorganic crystalline solid that has a narrowly defined chemical composition and characteristic physical properties. 2. In which three ways do minerals differ? Minerals differ by chemical composition, crystalline structure and physical properties. 3. What do the protons, neutrons and electrons indicate about an element? Electrons determine how the atom interacts with other atoms. Protons determine the atomic number and the number of electrons present when neutrally charged. Neutrons can vary in number, which determine which isotope of the element is present. 4. What is the difference between an isotope and an ion? a. An ion is an electrically-charged atom produced by adding (anion) or reducing (cation) the number of electrons present. b. An isotope is an element that differs by the number of neutrons present in the nucleus. 5. Identify the four types of bonds that can exist between atoms and state the significance of each. a. Ionic: transfer of electrons creating an electrostatic attraction b. Covalent: sharing of electrons between atoms c. Metallic: metal to metal bonds d. Van der Waals: weak residual bond between more strongly-bonded layers 6. Identify the bonding for the following minerals: diamond, halite (rock salt), graphite, copper. Diamond: covalent bonding in 3-D Graphite: covalent bonding in one direction, van der Waals bonding between covalent bonded sheets Halite: ionic bonding Copper: metallic bonding 7. Explain the significance of this statement to minerals: Ordered internal atomic arrangement is externally manifested. The external form of a particular mineral is controlled by the internal arrangement of the atoms or its internal structure. 8. Why are most metals good thermal and electrical conductors? Metals possess electrons that are very mobile. Electrons in metals tend to be easier to remove from the outer shell. 9. What are the eight most common elements in the crust (from first to last)? Oxygen, Silicon, Aluminum, Iron, Calcium, Sodium, Potassium and Magnesium. 10. What are the eight mineral groups? Which criteria are the mineral groups based upon? Silicates, Carbonates, Native Elements, Sulfides, Oxides, Sulfates, Halides and Phosphates. These groups are classified by anionic endings. 11. List the physical properties of minerals? Why must you rely upon more than the color of the mineral to identify it? Color, streak, luster, hardness, fracture, cleavage, specific gravity, crystal form, and tenacity. Other minor properties include taste, feel, magnetism, fluorescence and effervescence. Ex. Hematite can be brown, red or silver metallic, yet it always produces a red-brown streak. 12. How does cleavage relate to the internal structure of the mineral? Breakage or splitting occurs along smooth plane or planes of weakness determined by the strength of the bonds within individual mineral crystals. 13. What causes variation within a specific mineral? Some minerals have a specific chemical formula; others have a range of compositions. Galena (PbS) vs. Plagioclase Feldspar, which ranges from calcium-rich (CaAl2Si2O8) to sodium-rich varieties (NaAl2Si2O8). The mineral is dependent upon the ratio of calcium to sodium. Also, some minerals have the same chemical composition but different bonding or crystalline structures (diamond vs. graphite; gypsum vs. selenite) 14. Which group of minerals is the most abundant? The silicates 15. The ten minerals in Moh’s Hardness Scale. talc, selenite (or gypsum), calcite, fluorite, apatite, orthoclase, quartz, topaz, corundum and diamond Mineral Groups-Chapter 3 Mineral Group Anionic Ending Rock Association (s) Mineral Example Silicates Hornblende (pyroxene) (Ca,Na)2-3(Mg, Fe, Al)5Si6(Si, Al)2 O22(OH)2 Augite (amphibole) Quartz SiO Plagioclase Feldspar NaAlSi3O8 Potassium Feldspar CaAl2Si2O8 Mica (biotite) (muscovite) Olivene Carbonates Calcite Dolomite Sulfides Pyrite Galena Chalcopyrite Sulfates Anhydrite Gypsum Selenite Oxides Magnetite Hematite K Halides Halite Fluorite Native elements Copper Gold Silver Graphite Diamond