The earth is made of rocks, which are in turn made ofminerals. In this part of the course well learn howto identify common minerals and rocks.In order for something to be classified as a mineral, itmust meet five (5) criterion:Minerals are:· 1. Naturally occurring,· 2. Inorganic,· 3. Have known chemical compositions· 4. Have definite physical properties.5. Are solid· They are usually (although not always) crystalline.
Mineral ClassificationMinerals are classified based on chemical composition and crystal structure.Minerals are made of different ions bonded together.Ions are charged atoms• Cations are positively charged whereas• Anions are negatively charged Common ions in earths crust:O - most common ion (anion)Si, Al, Fe, Ca, Na, K, Mg, (Cations)Minerals are made mainly of these ions Crystal structureCrystal structure depends on sizes of and charges on ionsPolymorphs -- same chemical composition, different crystal structures Mafic silicate mineralsMost common minerals are silicates
Crystal structureCrystal structure depends on sizes of and charges onions Most common mineral group is the silicatesAll silicate minerals contain silicon and oxygen1. Mafic silicate minerals contain iron or magnesium andare dark in color.Examples: olivine, pyroxene, amphibole, and biotitemica2. Felsic silicates dont contain magnesium or iron, andare light in color.Examples: feldspar, quartz, clay minerals, muscovite
Silicate mineral structuresBasic building block: silica tetrahedronSilica tetrahedron is a silicon ion bonded to 4 oxygen ionsSilicon is positively charged (+4)Oxygen is negatively charged (-2)Net charge on tetrahedron: -4Because entire tetrahedron is negatively charged, it isattracted to cationsTetrahedra may link together by a cation (e.g. Mg, Fe, Na,Ca, K) serving as a bridge, or may link together bysharing oxygens
Isolated tetrahedral structureCations serve as links between tetrahedra; no sharing of oxygense.g. olivine, and garnet, which also happen to be mafic silicates Single chain silicatesAdjacent tetrahedra form a chain by sharing 2 of their oxygens withneighboring tetrahedrae.g. pyroxenes, which also happen to be mafic silicates Double chain silicatesTwo chains can link up by sharing oxygense.g. amphiboles, which are mafic silicates too Sheet silicatesSheets are formed when each tetrahedron shares 3 of its oxygens with itsneighborse.g. micas, biotite (mafic) and muscovite (non-mafic), and clay minerals, whichare non-mafic silicates Framework silicatesEvery oxygen in each tetrahedron is shared to form 3-D frameworke.g. feldspar, quartz, which are also non-mafic
Common non-silicate mineralsFluorite – used as a toothpaste additiveCalcite -- calcium carbonate -- Limestone is made of calcite.Dolomite -- calcium magnesium carbonateGypsum -- calcium sulfateGalena -- lead sulfidePyrite -- iron sulfideHalite -- sodium chloride (table salt)
How to Identify Minerals: Physical PropertiesGeologists determine the identity of an unknown mineral by describing itsphysical properties. They then use a reference book to find out whatmineral has those properties. We will learn to describe the physicalproperties. 1. Habit refers to the overall shape of the mineral. Scientists use termslike: "equant" (3 dimensions of the mineral have about the samelength, like a cube or sphere), “elongate" (one direction is long butthe other 2 are short, like a pencil), or "platy" (one dimension isshort, other 2 are long like a sheet of paper)Isolated tetrahedra & framework silicate minerals tend to be equantin habit; chain silicates tend to be elongate, sheet silicates are platy 2. Luster refers to the light reflected off of the mineral and its overallquality. Minerals can be termed: glassy, opaque, transparent, shiny,or most commonly: metallic and non-metallic.One of the first determinations a geologist must make is whether themineral in metallic or non-metallic.
CleavageRefers to very smooth, flat, shiny breakage surfacesThese special breakage surfaces correspond to zones ofweak bonding in the crystal structure.To describe cleavage, one must determine the number ofunique cleavage planes (directions) and their angle withrespect to each other (e.g. salt breaks into cubes, withcleavage in 3 directions, all at 90 degrees) NOcleavage
HardnessRefers to "scratchability" or resistance to being scratched. Harderminerals will scratch softer minerals.Geologists rank minerals according to hardness using the Mohs scaleMohs Hardness Scale (Commit this to memory)1.0 TALC2.0 GYPSUM2.5 FINGERNAIL3.0 CALCITE3.5 COPPER PENNY4.0 FLUORITE (Note the spelling!)5.0 APATITE5.5 STEEL KNIFE BLADE/GLASS PLATE6.0 ORTHOCLASE FELDSPAR7.0 QUARTZ8.0 TOPAZ9.0 CORUNDUM (RUBY)10.0 DIAMOND
ColorVaries in many minerals, e.g. quartzVERY unreliable.Some minerals come in just one color;other are many colors/many varieties. StreakRefers to color of mark left by rubbing mineral against astreak plate (unglazed porcelain). Streak does not varyeven if color does. Other PropertiesSome minerals are magnetic (i.e., magnetite)Some minerals effervesce ("fizz") in dilute acid (calcite)Specific gravity (like density) galena has a high specificgravity.
Pertinent Web SitesAmateur Mineralogy LinksA very extensive listing of links to sites related to mineralogy.Ask a GeologistIf you have questions, a professional geologist is here to help.Ecole des Mines de Paris MineralogyHere are some beautiful mineral pictures from a museum in Paris.Gems and Precious StonesJill Banfields (University of Wisconsin-Madison) integrated body of information about gems and gemstones.Gold InstituteA good commercial site with a lot of information about gold.Gold ProspectingA good source for information about recreational gold prospecting.Mineral and Gemstone KingdomThis site contains a comprehensive list of minerals and their properties.Mineral and Rock Description (National Park Service)Mineral and rock photographs and descriptions from the National Park Service.Mineral Data LinksLinks to several mineralogy related Web sites.Mineral Descriptions and ImagesThe Mineral Gallery is a constantly growing collection of mineral descriptions, images, and specimens, together with several ways ofaccessing these descriptions.Mineralogy and Petrology Research on the WebAn extensive list of mineralogy and petrology resources on the Web.Mineralogy DatabaseThis extensive mineral database contains more than 5,000 pages of mineral data. There are 3,874 individual mineral species datadescriptions.Mineralogy Links (University of Oxford)An extensive listing of mineralogy and minerals related sites.Mineral Identification TutorialMineral identification tutorial from Texas A & M University.Mineral PhotographsA comprehensive collection of mineral and gemstone photographs from The Image.Mineral Resources Program (USGS)The USGS Mineral Resources Program is responsible for providing and communicating current, unbiased information on the occurrence,quality, quantity, and availability of mineral resources.Minerals Links (Houghton Mifflin)
Minerals Links (NAGT)An extensive listing of mineral links arranged by topic from the National Association of Geology Teachers (NAGT).Minerals Links (University of Würzburg)An extensive listing of mineral links including mineral descriptions and thin section images.Minerals (Mineralogical Society of America)The Mineralogical Society of America web site offers a good, general description of mineral properties, classification, etc. directed primarilytoward K-12 grade students.Minerals (Trinity Mineral Company)Beautiful photos of rare minerals offered for sale by the Trinity Mineral Company.Minerals Information (USGS)United States Geologic Survey (USGS) statistics and information on the worldwide supply, demand, and flow of minerals and materials essentialto the U.S. economy, the national security, and protection of the environment.Minerals on the InternetA wide variety of minerals-related sites sorted into relevant categories from Tasa Graphic Arts, Inc.Mining and Mineral ResourcesA great source for information about mining of mineral resources, mining news and trends, etc.National Mining AssociationThe National Mining Association (NMA) represents the mining industry, mining equipment manufacturers, and other mining-related businesses,throughout the United States.Periodic Table of the ElementsIn addition to listing a wealth of information about each element, this location also lists and describes numerous compounds.
Periodic Table of the Elements IIA great source for information on the elements.Resource Fact Sheets (USGS)United States Geological survey (USGS) activities in the natural resources theme area inventory the occurrence and assess the quantity andquality of natural resources. Activities also include monitoring changes to natural resources, understanding the processes that form and affectthem, and forecasting the changes that may be expected in the future.Resources from SpaceUniversity of Wisconsin course notes with links to several essays about resources from space.Resource SustainabilityAn essay that examines the future of Earths resources.Rock and Mineral Collecting (USGS)Selected references on rocks, minerals, and gemstones from the United States Geological Survey (USGS).Rockhounds Information PageThe Rockhounds Information Page offers many links to mineral and rock related Websites.Smithsonian Gem & Mineral CollectionImages of mineral and gemstone specimens found in the Smithsonian Institution. (Not an official Smithsonian site)Society for Mining, Metallurgy and Exploration, Inc.The Society for Mining, Metallurgy, and Exploration (SME) is an international society of professionals in the minerals industry.Society of Economic GeologistsThe Society of Economic Geologists, Inc. (SEG) is an international organization of individual members with interests in the field of economicgeology.State Minerals Information (USGS)Statistics and information on the supply, demand, and flow of minerals and materials essential to the U.S. economy, the national security, andprotection of the environment from the United States Geological Survey (USGS).
Technical University of ClausthalThis site at a German university also shows some excellent mineral pictures.Virtual Atlas of Opaque and Ore MineralsThis site provides over 400 full colour photomicrographs of the major ore-forming associations and opaque minerals in non-mineralizedrocks. It describes typical examples of each material from many classical localities throughout the world. For each association there is alisting of the major (and important minor) primary ore minerals, alteration products and gangue, typical textures, a brief discussion of thegeology of the association and a list of references.World Lecture Hall (University of Texas at Austin)The World Lecture Hall features links to online courses in the United States and Canada.Simplest to use for Mineral I.D. Lab:Virtual Rock Baghttp://comp.uark.edu/~sboss/vrockbag.htm#minerals