How to identify a mineral 3

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Minerals Take-Away Points Chemical elements form in stars Atoms bond by sharing electrons Minerals are classified by their chemistry Minerals can be identified by their physical properties = atomic structure Silicates are the most important mineral group Crystals are determined by mathematical rules called symmetry Composition of the Sun Chemical elements form in stars Composition of the Sun • Abundance of Light Elements • Rarity of Lithium, Beryllium, Boron • Preference for Even Numbers • Abundance peak at Iron, trailing off after Chemical elements form in stars How Elements Form in Stars • • • • • • • Sun: H  He He + particle  Mass – Unstable He + He  Mass – Unstable He + He + He  C Add more He to make heavier elements End of the line is iron for energy production Atoms beyond Iron made in massive stars Chemical elements form in stars What are Planets Made of? • Same material as Sun • Minus the elements that remain mostly in gases • We find this pattern in a certain class of meteorites Chemical elements form in stars Chondrites Chemical elements form in stars The Earth’s Crust looks Very Different Chemical elements form in stars Composition of the Crust Chemical elements form in stars Minerals are the Chemicals that make up the Earth • Naturally Occurring • Inorganic • Chemical Compounds • About 5000 Known • 200 Common • 20 Rock-Forming One Type of Asbestos Silicates are the most important mineral group Tectosilicates - ThreeDimensional Networks • Quartz Feldspars Silicates are the most important mineral group Making Sense of Crystals Crystals are determined by mathematical rules called symmetry Unit Cells All repeating patterns can be described in terms of repeating boxes The problem in Crystallography is to reason from the outward shape to the unit cell Crystals are determined by mathematical rules called symmetry Which Shape Makes Each Stack? Crystals are determined by mathematical rules called symmetry Stacking Cubes Crystals are determined by mathematical rules called symmetry Crystals are determined by mathematical rules called symmetry Crystals are determined by mathematical rules called symmetry Crystals are determined by mathematical rules called symmetry Some shapes that result from stacking cubes Crystals are determined by mathematical rules called symmetry Symmetry – the rules behind the shapes Crystals are determined by mathematical rules called symmetry Symmetry – the rules behind the shapes Crystals are determined by mathematical rules called symmetry The Crystal Classes Crystals are determined by mathematical rules called symmetry Take-Away Points Chemical elements form in stars Atoms bond by sharing electrons Minerals are classified by their chemistry Minerals can be identified by their physical properties = atomic structure Silicates are the most important mineral group Crystals are determined by mathematical rules called symmetry [...]... Resinous, waxy, silky, etc are selfexplanatory • Vitreous is often used for glassy luster 4 Minerals can be identified by their physical properties = atomic structure Cleavage • Tendency to split along smooth planes of weaknessbetween atoms in crystal • Directly related to atomic structure • Related to Crystal Form • Every cleavage face is a possible crystal face • Not every crystal face is a cleavage face... to: • Weathering, ‘Chalk' marks • Breaking vs Scratching 4 Minerals can be identified by their physical properties = atomic structure Mohs vs Knoop Scales 1 2 3 4 5 6 7 8 9 10 Talc: Gypsum, Fingernail: Calcite, Penny: Fluorite: Apatite: Feldspar, Glass: Quartz: Topaz: Corundum: Diamond: very small 30 135 1 63 430 560 820 134 0 2100 7000 4 Minerals can be identified by their physical properties = atomic... related to masses of component atoms and their spacing • Usually very consistent 4 Minerals can be identified by their physical properties = atomic structure Density - gm/cm3 (weight relative to water ) • Air: 0.001 Wood - Balsa: 0.1, Pine: 0.5, Oak: 0.6-0.9 Gasoline: 0.7, Motor Oil: 0.9 Ice: 0.92 Water: 1.00 Sugar: 1.59 Halite: 2.18 Quartz: 2.65 Most Major Minerals: 2.6 -3. 0 Aluminum: 2.7 4 Minerals... Complex Anions (Radicals) • Many minerals contain groups of atoms that behave as single units 2 Atoms bond by sharing electrons NAMING MINERALS COLOR • Glauconite (Greek: Glaucos = Blue-green) OTHER PROPERTIES, USES • Magnetite COMPONENTS • Chromite PLACES • Muscovite (Moscow) PEOPLE • Biotite Chemicals (and Minerals) Are Classified by their Anions 3 Minerals are classified by their chemistry For Example:... chemistry Identifying Minerals 4 Minerals can be identified by their physical properties Identifying Minerals • • • • • • Color: very variable, complex causes Hardness: strength of atomic bonds Density: mass and spacing of atoms Luster: how electrons interact with light Cleavage: weak atomic planes Crystal Form: extremely useful but not for beginners • Other properties distinctive at times 4 Minerals can... by sharing electrons Summary of Bonding • Ionic bonding holds rocks and minerals together • Covalent bonding holds people and other organisms together • Metallic bonding holds civilization together • Hydrogen bonding gives water its heatretaining and solvent properties 2 Atoms bond by sharing electrons 4 Lattices • Atoms in crystals form a repeating pattern called a Lattice 2 Atoms bond by sharing...Atomic Bonding 1 IONS 2 Atoms bond by sharing electrons Atomic Bonding 2 Electrical Neutrality • (+) and (-) Cancel Out 3 Bonding (Satisfy 1 & 2) • Ionic (NaCl) • Covalent (O2) • Metallic (Cu, Al, Fe) • Hydrogen (in water) 2 Atoms bond by sharing electrons Ionic and Covalent Bonding 2 Atoms bond by sharing electrons Metallic Bonding 2 Atoms bond by sharing electrons Hydrogen Bonding 2 Atoms bond... face Quartz commonly forms crystals but lacks cleavage 4 Minerals can be identified by their physical properties = atomic structure Other Properties Crystal Form • Takes Luck & Practice • Well-formed crystals are uncommon • Crystal Classification is somewhat subtle Fracture 4 Minerals can be identified by their physical properties = atomic structure Identifying Minerals Geologic Setting • Some minerals... physical properties = atomic structure Color • Sometimes Distinctive • Often Unreliable • Affected By: – – – – Chemical Impurities Surface Coating Grain Size Weathering 4 Minerals can be identified by their physical properties = atomic structure Hardness • Resistance to Scratching • Directly related to relative strength of atomic bonds • Scratch Test (Mohs) • Indentation Test (Knoop) Common Errors due to: ... Have Little in Common • Fe: Gray, Metallic • FeCl2: Light Green, Water Soluble • FeSO4: Light Green, Water Soluble • FeCO3: Brown, Fizzes in Acid • FeS2: Dense, Brittle, Metallic, Cubic Crystals 3 Minerals are classified by their chemistry On the Other Hand, Sulfides have Many Properties in Common • FeS2 • CuFeS2 • PbS • ZnS2 All are Dense, Brittle, Metallic, have Cubic Crystals 3 Minerals are classified
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