GEOL 101 Properties Of Minerals
GEOL 101 Properties Of Minerals GEOL 101
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This 4 page Class Notes was uploaded by Victoria Williams on Saturday February 20, 2016. The Class Notes belongs to GEOL 101 at George Mason University taught by Mark Uhen in Fall 2016. Since its upload, it has received 24 views. For similar materials see Introductory Geology in Geology at George Mason University.
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Date Created: 02/20/16
Minerals What are they 0 Naturally occurring 0 Solid substance at earth surface temperature 0 Orderly crystalline structure 0 Well defined chemical composition ex Garnet Fe3A12SiO43 Quartz SiOz 0 Generally inorganic organic chains of carbon living Elements An element is a substance that can t be broken down into simpler substances by physical or chemical means Elements are differentiated by their atomic number which is the number of protons in the nucleus Minerals are made of Elements Atomic structure The nucleus is composed of protons charge and neutrons no charge The number of protons defines the elements Full electron shells have 2 first or 8 all others electrons Those that aren t full tend to react to form compounds 2316 Lecture Minerals Atomic Structure continued Isotopes The nuclei of the three isotopes of hydrogen Example Hydrogen One proton in the nucleus no neutrons is a Protium One proton one neutron is a Deuterium One proton two neutrons is a Tritium The addition of neutrons does not change what the element is but it adds weight to the atom and thus changes how it behaves Ionic Bonds Cation is the atom that gives up an electron to the atom its bonding with The Anion is the atom that takes the electron given by the Cation Covalent Bonds Sharing electrons not giving up any electrons just sharing them Metallic Bonds A ton of atoms share a ton of electrons between each other The electrons ow through the web of atoms As Uhen said it s the communist of atomic bonds Mineral Formation Crystallization The formation of a crystal like when salt water evaporates and leaves behind salt Halite Another example a hot water geyser that has a ton of minerals dissolved in it will spew out the water will evaporate and the minerals will crystallize One other example is cooling molten rock Agate Hollowed rocks that have hot mineral infused water injected into them The hot water will then cool and it cannot carry the minerals anymore so it deposits it in the hollowed rock Over time the minerals build up to create crystals like quartz Crystal Structure Halite along with a ton of other crystals form in cubes with perfect right angles Polymorphs Minerals with the same chemical composition but different crystal structures A Diamond B Graphite Different Polymorphs develop in different pressures and temperatures Properties of minerals Luster The freshly broken mineral Metallic luster looks like metal Some can look waxy looking like a bar of soap or candle wax We mostly either call them Metallic or NonMetallic Optical Quality Some minerals can be translucent seethrough like Quartz and Fluorite Quality can also be judged based on how it refracts light which can cause images to double up double refraction when you put it over the image But this is extremely rare Color streak Color is an extremely bad way to identify But when you get a powdered form of the mineral when you scratch the mineral against unpolished porcelain the powder can be a completely different color and can help identify the crystal Crystal Habit Fibrous Bladed Banded Cubic Crystals Different shapes that the minerals form into based on where they are developed Some crystals form in only a few habits 0 Tenacity The ability to change the shape of the mineral You can bend some and they will bounce back into shape You can bend others and they will stay bend Others might just snap in half and some might not bend at all 0 Hardness Mohs scale of hardness where diamonds are the hardest and talc is the softest To judge the hardness take a known mineral and try to scratch against the unknown mineral If the known mineral scratches the unknown then the unknown is softer on Mohs scale Keep testing materials with a known hardness to see which scratch each other to determine the identity of the unknown material 0 Cleavage and fracture Some crystals will break in certain ways based on where there are strong atomic bonds and weak atomic bonds Like if the horizontal bonds are weak then the crystal will fracture into sheets Example Crystals with cleavage in one direction will l ol gff i ig a e onwme break into sheets Crystals with two 1 cleavage planes at 90 degrees will break into rectangular shapes Crystals with two Single chain Mme cleavage planes can have different angles at Strumure grow which the cleavage meets like 120 degrees and 60 degrees and that will cause a sharp angled polygon There is also irregular D s fgi jlquot REESEme fracture a mineral that breaks into irregular shapes Then there s the chonchodial fracture where it can break and might look 7 233335 like swirls Mineral Classifications 0 Silicates are the most common minerals Quartz Feldspar group Framework Silicate They form in SiliconOxygen tetrahedrons structure which are easy to form They then form into these structures gt 0 Silicates make up most of earth s crust and other parts of the inside 0 Light Colored Silicates Feldspars Potassium feldspar Quartz Muscovite Clays Dark Colored Silicates Olivine olive green color Pyroxenes Amphiboles Biotite a dark form of muscovite because it has iron and magnesium in it Garnet forms in metamorphic environments W heat and pressure NonSilicate Materials Do NOT have the SiliconOxygen tetrahedrons gtgtgt NonSilicates Calcite most common nonsilicate carbonates CaCO3 reacts With acid marine organisms make their skeletons out of it Fluorite Halite in sea water Gypsum also found in sea water Hematite Fe203 makes a red streak on a streak plate Chalcopyrite CuFeSz Sulfur S element