Rock samples of pebble to cobble size are used in the every pebble tells a story activity

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Every Pebble Tells a Story L Braile, Purdue University S Braile, Happy Hollow School, West Lafayette, IN March, 2006 NSTA, Anaheim, 2006 braile@purdue.edu, http://web.ics.purdue.edu/~braile Last modified March 13, 2006 The web page for this document is: http://web.ics.purdue.edu/~braile/edumod/pebble/pebble.htm This PowerPoint file: http://web.ics.purdue.edu/~braile/edumod/pebble/pebble.ppt Partial funding for this development provided by the National Science Foundation  Copyright 2005 L Braile Permission granted for reproduction for non-commercial uses Objectives: Make inferences about the geological history of a pebble by observing its characteristics and by utilizing geological principles and concepts The Every Pebble Tells a Story* activity is an excellent follow-up to the study of mineral and rock identification However, extensive experience with mineral and rock identification is not required This activity provides practice in observing and critical thinking and opportunities for sketching and creative writing Because students select, analyze and write about their own pebble, we have found that the activity is very engaging for students Additional materials (http:// web.ics.purdue.edu/~braile/edumod/pebble/pebbleAM.htm) that accompany this activity include resources for the teacher, for helping the student with the interpretation of their rock sample, and for mineral and rock identification Rock Samples of pebble to cobble size are used in the Every Pebble Tells a Story activity Limestone Sandstone Quartzite pebbles Basalt Pebbles with cross-bedding Conglomerate Mineral identification is an excellent preparatory exercise for the Every Pebble Tells a Story activity Quartz Hematite Olivine As a practice or review exercise, try to identify one or more mineral samples List two distinctive properties of your mineral sample Use the following Mineral Identification Flowchart to identify your mineral sample What is the name of your mineral sample? An online mineral identification quiz can be found at: http://www.soes.soton.ac.uk/resources/collection/minerals/min-quiz/index.htm Mineral Identification Flowchart Magnetic; shiny blac k Metallic Luster Magnetite Silver color Nonmagnetic Mineral Identification Flowchart Gold color Harder than steel nail Poor Cleavage Nonmetallic Luster; Dark color Softer than steel nail Sta rt here Good Cleavage Harder than steel nail Good Cleavage Poor Cleavage Cleavage Softer than fingernail Gr aphite Reddish brown s treak Hem atite Harder than f ingernail, dense Galena 56 o and 124 o angle s Am phibole (hornblende) 87 o and 93 o angles Pyroxene (augite) Well-f ormed crystals No c rystals, glassy, olive green Nonmetallic Luster; Light color Softer than f in gernail Cubic cleavage Gar net Olivine One direction, sheets Biotite m ica Reddish brow n streak Hem atite Striations (tw inning) Plagioclase feldspar No s triations (tw in ning) Or thoclase feldspar No cleavage Softer than steel nail, harder than f in gernail Pyrite Quartz Halite Pow der reacts with HCl Dolom ite Sample reacts w ith HCl Calcite Good Cleavage Thin sheets Muscovite m ica Thick sheets Gypsum (selenite ) Poor Cleavage “Greasy ” feel Talc “Nongreasy ” feel Gypsum (alabas ter ) Non-cubic cleavage (modif ied from D.J Thompson, Basic Geology: Lab Manual , Allegheny Press, 1986; and D.J Conte, D.J Thompson and L.L Moses, Earth Scienc e - A Holistic Approach, W.C Pebbles for “Every Pebble Tells a Story” activity Observing pebble features Simplified Rock Identification and Origin** Flowchart Simplified Rock Identification and Origin Flowchart (designed primarily to determine the origin of the rock sample – igneous, sedimentary or metamorphic) Visible, coarse grain, foliation (wavy layers), grains are aligned, often has “salt and pepper” look, white “veins”, most grains are harder than a nail Coarse to fine grain, surface is shiny, foliation (wavy or flat layers), softer than a nail Rock has layers* Rock has distinct “sugary” look, layering may be very subtle, cannot scratch off grains, harder than nail, white to tan, sometimes colored, may show cross bedding Fine grain, surface is not shiny, thin flat layers, usually dark color Grains are fragments (often rounded) cemented together, can usually scratch off grains Very fine grain, looks “chalky” but is very hard (harder than nail), can be any color, layering may be very subtle Start Here Rock has no layers* METAMORPHIC, gneiss METAMORPHIC, schist (coarse grain), phyllite (medium grain), slate (fine grain, less shiny, thin flat layers) METAMORPHIC, quartzite SEDIMENTARY, may have fossils, shale, mudstone SEDIMENTARY, may have fossils, siltstone, (fine grain), sandstone (medium grain), conglomerate (contains rounded pebbles), breccia (contains angular pebbles) SEDIMENTARY, chert, flint Soft***, reacts with acid, may have fossils, usually light gray, SEDIMENTARY, limestone Fine grain, no crystals visible Grains visible or many wavy lines, METAMORPHIC, marble+ Visible interlocking grains (crystal shapes), often “salt and pepper” appearance Hard***, does not react with acid, no fossils, usually dark color, IGNEOUS, volcanic Fine grain, no crystals visible, has vesicles (holes, like gas bubbles) Glassy, usually black IGNEOUS, plutonic, may contain xenoliths Rock has layers* Simplified Rock Identification and Origin Flowchart (designed primarily to determine the origin of the rock sample – igneous, sedimentary or metamorphic) sometimes colored, may show cross bedding Fine grain, surface is not shiny, thin flat layers, usually dark color Grains are fragments (often rounded) cemented together, can usually scratch off grains Very fine grain, looks “chalky” but is very hard (harder than nail), can be any color, layering may be very subtle Start Here Rock has no layers* fossils, shale, mudstone SEDIMENTARY, may have fossils, siltstone, (fine grain), sandstone (medium grain), conglomerate (contains rounded pebbles), breccia (contains angular pebbles) SEDIMENTARY, chert, flint Soft***, reacts with acid, may have fossils, usually light gray, SEDIMENTARY, limestone Fine grain, no crystals visible Grains visible or many wavy lines, METAMORPHIC, marble+ Visible interlocking grains (crystal shapes), often “salt and pepper” appearance Hard***, does not react with acid, no fossils, usually dark color, IGNEOUS, volcanic Fine grain, no crystals visible, has vesicles (holes, like gas bubbles) Glassy, usually black Fine grain matrix, distributed crystals (phenocrysts) visible (usually rectangular) IGNEOUS, plutonic, may contain xenoliths IGNEOUS, volcanic IGNEOUS, volcanic, obsidian IGNEOUS, volcanic This flowchart is designed for commonly occurring rocks, especially those that are fairly resistant to erosion (often igneous and metamorphic rocks) and are thus likely to be selected as pebbles for the Every Pebble Tells a Story activity A small percentage of volcanic rocks show small scale layering caused by flow lines; these and other samples may not be correctly classified using this flowchart Some samples show sedimentary features but have been metamorphosed Examples include metamorphosed conglomerate, quartzite and greenstone (a metamorphosed volcanic rock) * “Has layers” means thin layers in hand specimen ** Rock type and most recent origin of the rock (igneous, sedimentary, metamorphic) is inferred from the flowchart and can be interpreted in relation to the Rock Cycle *** “Hard” means hardness of >5; “soft” means hardness [...]... recrystallization of the original minerals in the parent rock and development of metamorphic texture b Metamorphic textures are alignment of rectangular, platy, and elongated crystals; development of shiny surfaces by the conversion of clay minerals to mica; the generation of metamorphic layering called foliation (“wavy” layering); injection of minerals (usually quartz and feldspar) in veins and dikes that often... Flowchart (designed primarily to determine the origin of the rock sample – igneous, sedimentary or metamorphic) Visible, coarse grain, foliation (wavy layers), grains are aligned, often has “salt and pepper” look, white “veins”, most grains are harder than a nail Coarse to fine grain, surface is shiny, foliation (wavy or flat layers), softer than a nail Rock has layers* Rock has distinct “sugary” look,... for the Every Pebble Tells a Story activity A small percentage of volcanic rocks show small scale layering caused by flow lines; these and other samples may not be correctly classified using this flowchart Some samples show sedimentary features but have been metamorphosed Examples include metamorphosed conglomerate, quartzite and greenstone (a metamorphosed volcanic rock) * “Has layers” means thin layers... colored** Rock has layers Rock is often hard* Gneiss (M)*** Coarse grained; often soft* Schist (M) Fine grained; often soft* Phyllite (M) Soft*; usually white, pink or tan Hard* Rock has no layers Rock is dark colored** Start here Rock Identification Flowchart Rock has crys tals (“coars e grained”) Layers are wide bands Fine grained matrix Rhyolite (I) Coarse grained Granite (I) Fine grained matrix; black,... distinct layers e Mineral sorting f Chemical sedimentary rocks (precipitation) g Clastic sedimentary rocks contain rock or mineral fragments h Veins, weathering, staining Common igneous processes and rock characteristics: a Melting, subsequent cooling resulting in crystals of distinct mineral types b Plutonic igneous rocks often show a “salt and pepper” appearance and interlocking crystals c Volcanic igneous... “sugary” look, layering may be very subtle, cannot scratch off grains, harder than nail, white to tan, sometimes colored, may show cross bedding Fine grain, surface is not shiny, thin flat layers, usually dark color Grains are fragments (often rounded) cemented together, can usually scratch off grains Very fine grain, looks “chalky” but is very hard (harder than nail), can be any color, layering may be very... gray Light gray Basalt (I) Andesite (I) Med grained; black, gray, greenish Diabase (I) Coarse grained; “salt and pepper” appearance Diorite (I) Coarse grained; black, gray, greenish Sand grains visible; feels like sandpaper Cannot scrape off sand grains, “sugary” Thin, flat layers; greenish, No sand grains gray, red; smooth visible; very fine grained Thin, wavy layers , looks like mudstone Rock has... (continued…) Try the Every Pebble Tells a Story activity with your own pebble Use the procedure and sample pages from the Every Pebble activity description and the flowcharts and other materials in the “Additional Materials” handout Mineral identification tables for more information on common mineral properties Mineral Key Metallic Minerals (all minerals have metallic Luster) Hardness 6 6 1-5 2.5... cemented together, can usually scratch off grains Very fine grain, looks “chalky” but is very hard (harder than nail), can be any color, layering may be very subtle Start Here Rock has no layers* fossils, shale, mudstone SEDIMENTARY, may have fossils, siltstone, (fine grain), sandstone (medium grain), conglomerate (contains rounded pebbles), breccia (contains angular pebbles) SEDIMENTARY, chert, flint Soft***,... Hilton, San Clemente Seismographs, Fri., 4/7, 2-3PM, CC 304C Every Pebble Tells a Story, Sat., 4/8, Hilton, El Capitan A CSTA (Oct 20-22, 2006, San Francisco):   Earthquakes – A One Day Workshop for Teachers, Sat., 10/21, 8AM-4:30PM Also, Earthquakes and the San Francisco Bay Area and Every Pebble Tells a Story NSTA (March 28, 2007, St Louis):  Earthquakes – A One Day Workshop for Teachers Every Pebble
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