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Gary Vorwald NYS Rock & Mineral Supervisor Paul J. Gelinas JHS [email protected] Event Description Participants will demonstrate their knowledge of rocks and minerals in this station-based event. A team of up to 2 Approximate time: 40 – 50 Minutes Event Parameters Each team may bring: one magnifying glass One 3-ring binder (1 inch) containing information in any form from any source Materials MUST be 3-hole punched and inserted into the rings (sheet protectors allowed) The Competition Station Event: 15-24 stations with samples & questions Equal time intervals will be allotted for each station. When the signal is given, participants will begin work at their initial station. Participants may not move to the next station until prompted to do so, may not skip stations, nor return to any previously-visited station Mineral and Rock Stations The Competition HCl will not be provided, nor may it be brought to, or be used during the competition. Written descriptions as to how a specimen might react were it to be tested with HCl may be provided. The Competition Identification will be limited to specimens appearing on the Official Science Olympiad Rock and Mineral List (see www.soinc.org) Other rocks or minerals may be used to illustrate key concepts. Tournament Directors may include up to five additional specimens important to their own state. If additional specimens are to be included, all teams must be notified no later than 3 weeks prior to the competition. 2017 Rock & Mineral List Available at: https://www. soinc.org Students should place list in front of notebook Minerals are organized by mineral family Consists of: 59 Minerals 7 Metamorphic Rocks 10 Igneous Rocks 17 Sedimentary Rocks (or varieties) Native Elements 16. Copper 18. Diamond 25. Gold 26. Graphite 50. Silver 54. Sulfur Sulfides 12. Bornite 15. Chalcopyrite 23. Galena 40. Pyrite 52. Sphalerite Halides 22. Fluorite 30. Halite Oxides / Hydroxides 8. Bauxite 17. Corundum 24. Goethite/ Limonite Minerals Silicates 6. Augite 10. Beryl 20. Epidote Carbonates, Borates 32. Hornblende 5. Aragonite 33. Kaolinite 7. Azurite 38. Olivine 13. Calcite 39. Opal 19. Dolomite 49. Rhodonite 36. Malachite 51. Sodalite 59. Ulexite 53. Staurolite 55. Talc Phosphates, Sulfates 56. Topaz 4. Apatite 57. Tourmaline 9. Barite 58. Tremolite 14. Celestite Garnet group 2. Almandine 31. Hematite 35. Magnetite Gypsum varieties: 27. Alabaster 28. Satin Spar 29. Selenite Mica Group 11. Biotite 34. Lepidolite 37. Muscovite Quartz varieties 41. Agate/Onyx 42. Amethyst 43. Chalcedony 44. Citrine 45. Crystal 46. Jasper 47. Milky Quartz Feldspar - Plagioclase 48. Rose Quartz Series 1. Albite Feldspar – potassium feldspar 3. Microcline [Amazonite] 21. Orthoclase Specimen numbers are the same as in previous and current Science Olympiad Rock and Mineral Kits that may be ordered from Wards Science Olympiad Kits. * Additional Minerals (Nationals only) Actinolite Kyanite Labradorite [plagioclase feldspar series] Pyrolusite Rhodochrosite Rutile Spodumene Stilbite Turquoise Zircon Labradorite feldspar Kyanite Zircon Rhodochrosite Rocks Sedimentary (cont) Metamorphic 60. Gneiss 61. Marble 62. Phyllite 63. Quartzite 64. Schist [Garnet] 65. Schist [Mica] 66. Slate Igneous 67. Andesite 68. Basalt 69. Diorite 70. Gabbro 71. Granite 72. Obsidian 73. Pegmatite 74. Pumice 75. Rhyolite 76. Scoria Sedimentary 78. Arkose 80. Breccia 81. Chert Coal Varieties: 77. Anthracite 79. Bituminous 86. Lignite 82. Conglomerate 84. Diatomite 85. Dolomite Rock or Dolostone 86. Lignite Coal Limestone varieties: 87. Chalk 83. Coquina 89. Fossiliferous limestone 90. Oolitic limestone 91. Travertine 92. Sandstone 93. Shale Coaching Tips: Choose team members from different grade levels to avoid having to train a completely new team the following year. Experience is a true advantage for those teams that remain on or near the top for many years running! Have your team practice with many real samples Compile a notebook that is easy to find information Visit local museums, mineral shows, etc. Coaching Tips: Notebooks Participant notebooks are an integral part of the R & M Event. The goal for permitting resources is to encourage conceptual development in lieu of memorization of facts. Notebooks provide a framework for learning, understanding, and quick reference. Participant-developed binders are generally more helpful during the event than field guides. Field guides are not permitted during the competition this year Coaching Tips: Notebooks Survey: Any size binder OR 1-inch binder (recommended by Earth Science Committee) Participants who construct their own note-books are generally better prepared. Due to time constraints, a well-organized notebook provides a much more efficient resource than most others. Coaching Tips: Notebooks Notebooks provide an opportunity to organize facts in a personalized format. Notebooks provide an opportunity to include information from many sources. Notebooks provide a quick and easy means of checking participant progress. WARNING! Events that permit resources are generally much more challenging than those that do not. This is done purposely! Suggested Notebook Contents Devote one page to each Rock or Mineral specimen. Alphabetize mineral section by mineral name; rocks by type, then alphabetical. Each page should include, but is not limited to: a. One or more colored images b. Mineral Group or Rock classification c. Environment(s) of formation d. Properties of the specimen e. Formula or composition f. Commercial use (Avoid too much info that results from printing web pages; info should be easy to find & understand) Suggested Notebook Contents (Alphabetized) glossary of important terms Mohs scale of hardness Mineral flow chart or ID Chart with Properties Rock charts: igneous, sedimentary, and metamorphic Bowen’s Reaction Series chart Rock cycle diagram Diagrams of common mineral crystal forms & habits State Minerals Resources Rock & Mineral kits Wards Science Rock and Mineral Kit Science Olympiad Rock & Mineral Kit (OLY01) ESES, P.O. Box 503, Lee’s Summit, MO 64063 $85/kit including shipping (purchase orders or check) Other Worlds Educational Enterprises – Rock and Mineral CD, Exam packets, Rock and Mineral Kits http://www.otherworlds-edu.com/RocksAndMinerals.htm Rock & Mineral Guides (Audubon, Simon & Schuster, Petersen, Golden) Science Olympiad Store http://store.soinc.org/default.aspx • Science Olympiad Student Center • Wiki - http://scioly.org/wiki/Rocks_and_Minerals • Practice exams • Scioly.org Test Exchange: http://scioly.org/wiki/Test_Exchange • Test Exchange Archive – http://scioly.org/wiki/index.php/2014_Test_Exchange • North Carolina Science Olympiad http://www.sciencenc.com/event-help/rocksandminerals.php • National Science Olympiad – event info • https://www.soinc.org/rocks_minerals_c Websites Mineral & Gemstone Kingdom - general info on thousands of minerals and gems http://www.minerals.net/ Mineral & Locality Database http://www.mindat.org/ USGS Educational Resources for Secondary Grades (7–12) – click on Rocks and Minerals to get dozens of links http://education.usgs.gov/secondary.html#rocks Rocks for Kids – info on mineral properties & characteristics http://www.rocksforkids.com/RFK/identification.html Geoman’s Mineral & Rock Charts http://jersey.uoregon.edu/~mstrick/MinRockID/MinRockIndex.html 3 Basic Types of Rocks (Ask GeoMan) http://jersey.uoregon.edu/~mstrick/AskGeoMan/geoQuerry13.html James St John, Ohio State University Homepage – go to his links for Common Rocks, Common Minerals, and Sediments for good descriptions & images http://www.newark.osu.edu/facultystaff/personal/jstjohn/Documents/Home-page.htmmes Sample Event Questions STATION 1 1. Identify Mineral A. A. Emerald B. Beryl 2. Identify Mineral B. A. Hornblende B. Augite C. Tourmaline D. Olivine C. Apatite D. Tourmaline E. Apatite E. Topaz Sample A (Beryl) 3. Observe the properties of the minerals. Which statement best describes the differences between them? A.Sample A has about the same density as Sample B. B.Sample A is harder than Sample B. C. Sample A has a sub-metallic luster while Sample B is vitreous. D. Sample A is hexagonal while Sample B is a prismatic crystal. 4. What is a use for Mineral B? A.Fine quality crystals are cut into faceted semi-precious gems. B.It is used as an abrasive because of its extreme hardness. C. It is a common rock-forming mineral found in many igneous and metamorphic rocks. D. It is a source of beryllium. Sample B (Tourmaline) STATION 2 5. What is the texture of igneous Rock A? A.fine-grained C coarse-grained B. glassy D. vesicular 6. What is the name of Rock B? A.Gabbro C. Diorite B.Granite D. Andesite Sample A (Obsidian) 7. What is the name of Rock C ? A.Gabbro C. Diorite B.Granite D. Andesite Sample B (Granite) 8. Which rock cooled at the fastest rate? A B C 9. Which minerals are characteristic of Rock C? A. Orthoclase feldspar & quartz B. Plagioclase Feldspar & Olivine C. Quartz & Olivine D. Plagioclase Feldspar & Hornblende Sample C (Diorite Mineral Definition More than 4,000 naturally occurring minerals—inorganic solids that have a characteristic chemical composition and specific crystal structure—have been found on Earth. A substance needs to meet the following criteria to be considered a mineral: Naturally occurring Inorganic Solid Definite chemical composition Orderly internal crystal structure Physical Properties of Minerals Each mineral has different physical and chemical properties which allow it to be identified. Many of the more common properties are addressed in the following slides. Mineral Properties Color Color varieties of corundum (sapphire) Some Minerals Have a Distinct Color Azurite Copper Pyrite Gold Sulfur Malachite Color - tourmaline Color may be helpful but other properties are needed because: The same mineral has many color varieties Color Halite Selenite Gypsum Different minerals have the same color or are colorless! Calcite Quartz Luster the way a mineral reflects light Two General Types: Metallic & Nonmetallic Metallic – shines like a metal Can be dull metallic as in magnetite Luster Nonmetallic – doesn’t shine like a metal; many types including adamantine, vitreous (glassy), dull/earthy, silky, waxy, resinous, pearly, & greasy Adamantine Vitreous (glassy) Silky Earthy (dull) Waxy Resinous Cleavage vs Fracture -the way a mineral breaks when stressed Cleavage – breakage in flat surfaces along planes of weakness Several basic forms based on # directions One direction (basal) Two directional Three directional (not at right angles; rhombic) Three directional (right angles or cubic) Octohedral (4 – directions) Cleavage examples: Basal (Muscovite) Cubic (Galena) Two Directions (Feldspar) Rhombohedral (Calcite) Octohedral (Fluorite) Types of Fracture -breaks in random directions (no planes of weakness) Conchoidal (shell like) - Quartz Hackly (jagged edges) - Copper Fibrous (narrow splinters) - asbestos Uneven - Kaolinite Hardness – minerals ability to resist scratching Moh’s Scale of Hardness Relative scale 1 is softest; 10 is hardest Harder minerals will scratch softer ones http://www.mineralogicalassociation.ca/young/images_page/Hardness.jpg Streak - powdered color of a mineral; non-metallic minerals usually have white or no streak; metallic minerals have colored streak Streak Color for a Few Common Minerals Black - Graphite Black - Pryite Black - Magnetite Black - Chalcopyrite Gray - Galena Limonite - Yellow-brown Hematite - Red-brown Specific Gravity or Density S.G. - Ratio of density of mineral compared to density of water Can be determined by weighing mineral suspended in water Can also be calculated by determining the mass and volume of a mineral (density) Light - Minerals with S.G. less than 2 Medium – S.G. 2-4.5 Heavy – S.G. Greater than 4.5 Most silicates are 2.5-3.0 Most metallic minerals are heavy Gold has a S.G. of 19.3! Crystal Form (system) – the geometric shape that crystals form in ideal conditions; there are 6 generally accepted forms based on symmetry, but these are very difficult to determine without advanced study. In NYS, we will only require two of these: cubic (isometric) and hexagonal. Cubic - pyrite Hexagonal quartz Crystal Systems All minerals can be divided into one of six crystal systems based on symmetry. These systems use three or four imaginary lines, called axes, to define the system based on the length of the axis and the angle that the axes intersect. Understanding crystal systems is very complex, and often can not be determined by simple observation of a crystal. Students should be able to indicate the crystal system for each mineral based on their research and their notes. Identifying crystal systems will NOT be required in New York competitions except for isometric (cubic) and hexagonal. Mineral Habit – visible external shape of a mineral Examples include acicular, bladed, prismatic, hexagonal, cubic, rosette, botryoidal, striated, massive, radiating, twinning, & granular. Twinning - staurolite Acicular (needlelike) - actinolite See Crystal Habit in Wikipedia for examples http://en.wikipedia.org/wiki/Crystal_habit Mineral Habits Botryoidal - hematite Bladed - kyanite Prismatic Massive Rosette – barite rose Transparency (diaphaneity) Transparent Translucent Opaque Special Properties Magnetism magnetite Double Refraction (birefringence) - calcite Fluorescence Mineral Properties are determined by the arrangement of the atoms Chart at right shows the atomic arrangement of several silicate minerals and how it influences breakage patterns (cleavage or fracture) Mineral Classification – minerals are grouped into families based on chemical composition Native elements – minerals made of a single element. Ex. copper, gold, graphite, sulfur, silver Oxides – combination of a metal & oxygen, common ore minerals. Ex. Hematite (Fe), corundum (Al) Silicates - made from metals combined with silicon and oxygen; largest group of minerals; silicon tetrahedron structure, most common mineral family, many subgroups; some are very complex. Ex. Quartz, feldspars, micas, olivine, hornblende, tourmaline, garnets, augite, talc, epidote, etc. Sulfides: compounds of a metal with sulfur, common ore minerals. Ex. Galena (Pb), Sphalerite (Zn), Pyrite (Fe), Chalcopyrite & Bornite (Cu, Fe) Mineral Classification – cont. Sulfates : compounds of sulfur with metals and oxygen; contain SO4 ; often form in evaporite environments. Ex. Gypsum (calcium), barite (barium), celestite (strontium) Carbonates – minerals made of carbon, oxygen, and a metallic element (contain CO3); most fiz in acid. Ex. Calcite, dolomite, malachite. Phosphates: contain PO4 ; not as common. Ex. Apatite Halides – form from halogen elements (chlorine, fluorine) with metallic elements. Usually very soft and easily dissolved in water. Ex. Halite (NaCl) and fluorite. Formation of Minerals Minerals form in a variety of ways in different environments. Crystallization from melt (igneous rocks) Precipitation from water Evaporation of sea water forming chemical sedimentary rock such as gypsum rock salt Hydrothermal ore deposits (ex. gold veins) Chemical alteration during weathering or metamorphism Precipitation from a vapor – ex. Sulfur in a volcanic region Minerals as Resources (uses) Know how minerals are used and how they are non-renewable resources Ores - a mineral that contains enough of an element to make it economically feasible to extract and process. Ex. Pyrite (sulfur), Galena (lead), Hematite (iron), Bauxite (aluminum), Sphalerite (zinc) Minerals are used in every day life for everything from food supplements, manufacturing, jewelry, building materials, electronics, ornamental objects, etc. Students should know the uses of every mineral on list. Websites: Northwest Mining Association http://www.nwma.org/education/Uses%20for%20Minerals.htm Geology .com http://geology.com/minerals/ Gem Minerals Semi-precious vs precious stones Mineral & their gem varieties ex. Beryl: Aquamarine – blue-green Emerald – green Morganite – pink Corundum: Sapphire –blue, multiple colors Ruby - red Rocks A rock is an aggregate of one or more minerals. Rocks are the building blocks of the Earth's crust. Rocks Igneous - crystallized from hot, molten rock Examples: granite, basalt, pumice, obsidian Sedimentary - fragments of sediment laid down by water or wind are compressed or cemented over time Examples: sandstone, shale, limestone Metamorphic - rocks changed by heat and or pressure or chemical activity Examples: gneiss, schist, slate, marble Rock Cycle http://rst.gsfc.nasa.gov/Sect2/rock_cycle_800x609.jpg Igneous Rocks The term igneous means "fire-formed." Igneous rocks crystallized from hot, molten magma or lava, as it cooled. Magma is hot, molten rock beneath the surface of the Earth. Lava is hot, molten rock that has flowed out and onto the surface of the Earth. Igneous rocks make up more than 90% of Earth's crust, by volume. Igneous Rocks Classified by Texture and Composition Texture of a rock is a description of its grain size. The rate of cooling influences the texture of igneous rocks. Composition of a rock depends on the minerals it contains Extrusive rocks (volcanic) - cooled quickly at earth’s surface): textures include fine grained (aphanitic), glassy, vesicular (holes from gases) Intrusive rocks (plutonic) cooled slowly beneath earth’s surface from magmaslow cooling = coarse grained Igneous Rocks Igneous Rock Textures Glassy – cools very fast; no crystals ex. obsidian & pumice Fine grained Obsidian showing glassy texture Pumice has glassy texture but often doesn’t look like glass due to holes from gases (Aphanitic) – crystals or grains smaller than 1 mm; cools relatively fast from lava ex. Basalt, rhyolite, andesite Basalt with illustrating uniform appearance of fine grained texture Basalt magnified 30 x under microscope showing fine crystals Igneous Rock Textures Coarse grained (Phaneritic) – crystals or grains larger than 1 mm; cools slowly from magma, allowing crystals to form. Ex. Granite, Diorite, Gabbro. Granite showing coarse grained texture with visible mineral crystals Pegmatite is very coarse grained, with minerals larger than 10 mm. Pegmatites are often the source of gem minerals. Specimen at left contains albite, muscovite, and a garnet crystal. Igneous Rock Textures Vesicular – fine grained or glassy rocks with holes from gases; rocks solidify very quickly. Ex: scoria, vesicular basalt, pumice Porphyritic – a mix of some coarse grained minerals in a fine matrix. Porphyry deposits are formed when a column of rising magma is cooled in two stages. In the first stage, the magma is cooled slowly deep in the crust, creating the large crystal grains. In the final stage, the magma is cooled rapidly at relatively shallow depth or as it erupts from a volcano, creating small grains that are usually invisible to the unaided eye. Igneous Environments of Formation Environment of Formation: Extrusive (Volcanic) Extrusive or volcanic rocks form from lava, which cooled quickly on the Earth's surface. Extrusive Rocks & Types of Volcanic Eruptions Mafic Lava Effusive eruptions with lava flows and little gas Oceanic crust Hot Spots Create shield volcanoes Rocks formed include basalt, scoria, basalt glass Ex. Hawaii Felsic/Andesitic Lava Explosive eruptions with lots of gas, volcanic ash, and pumice Pyroclastic flows Continental crust Ocean/Continent subduction zones Create strato-volcanoes Rocks formed include pumice, rhyolite, andesite, obsidian Ex. Mt. St Helens (above right) Mt. Pinatubo (bottom right) Intrusive Igneous Rocks Intrusive or plutonic igneous rocks formed from magma which cooled deep beneath the surface of the Earth. Examples: gabbro, diorite, granite Igneous Rocks Igneous Rocks – Composition Felsic (or sialic) - Rich in silicon, oxygen, and aluminum. Tends to have light-colored minerals such as quartz and potassium feldspar. Examples: granite, rhyolite. Intermediate - Intermediate in composition between felsic and mafic. Mixture of light and dark minerals. Examples: diorite, andesite. Mafic - Iron and magnesium rich. Typically dark-colored. Examples: gabbro, basalt. Composition of Igneous Rocks Bowen’s Reaction Series Intrusive Formations http://www.geogrify.net/GEO1/Lectures/Landforms/IgneousProcess.html Batholith - Creates topographic highs in mountainous regions. Landforms "massive" in character - lacking linear ridges & valleys. Rocks are coarse to very coarse grained; often granites and other phaneritic felsic rocks. Example: Idaho Batholith (16,000 mi2); Sierra Nevada Mountains (Yosemite) Text From: http://earthonlinemedia.com/ipg/outlines/lecture_igneous_rocks.html Exposed Batholith at Yosemite National Park, Sierra Nevada Mountains, California Dike - Magma cools in fractures that cut across host rock. Form linear ridges when exposed . Laccolith - Magma cools between layers and warps overlying host rock into mushroom shape. Forms domes Sill - Magma cools between layers of host rock. Example: Palisades Sill Dikes cutting across existing rocks Sill intruded parallel to rock layers Eroded laccolith Sedimentary Rocks Sedimentary rocks cover about 75% of the world's land area. Sedimentary rocks form when loose sediment (gravel, sand, silt, or clay) becomes compact-ed and/or cemented to form rock. The process of converting sediment to sedimentary rock is called lithification. Sediment is deposited in horizontal layers called beds or strata. Distinguishing Characteristics of Sedimentary Rocks Layers of sediments Fossils Grains cemented together Textures of Sedimentary Rocks Clastic – compacted & cemented rock fragments; sediment derived from continents. examples: Shale, sandstone, conglomerate, breccia Chemical/Biochemical (Crystalline) – examples: Gypsum, rock salt, dolostone, travertine limestone Organic (Bioclastic): examples: Limestone (oolitic, fossil); Coal (bituminous, anthracite) Sedimentary Rocks New York State Earth Science Reference Tables Mesa Community College Sedimentary Rock Classification: http://www.mesacc.edu/sites/default/files/pages/section/academic-departments/physical-science/geology/images/sedimentaryrkid1.jpg Clastic Inorganic Composed of clay minerals, quartz, feldspar, other mineral & rock fragments Formed by compaction & cementation of grains Rock fragments Continental Environments include rivers, alluvial fans, desert sand dunes, deltas, beaches, lakes Rock type depends on grain size Fossils may be present, particularly in shale and sandstone Breccia – angular fragments; mixed pebble size and smaller Sandstone – sand sized; mostly quartz Conglomerate – rounded fragments; mixed pebble size and smaller Shale – clay sized particles Organic Sedimentary Rocks Formed from remains of plants or animals Often monominerallic If limestone, fizz in acid Many types of limestones due to various environments May or may not have visible fossils Coal Composed of carbon Coal forms by compression and carbonization of plant material Bituminous Coal is most common Most coal formed 300 million year ago in swamp environments where vegetation was abundant Anthracite Coal is the most pure form of coal (92-98% carbon) and burns the most efficiently. It formed during mountain building episodes when bituminous coal was under heat and pressure. It is often considered a metamorphic rock, but is still found in sedimentary sequences of sandstone and shale. Bituminous Coal Anthracite Coal Types of Limestone Composed of calcum carbonate (calcite or aragonite) Most formed in marine environment from skeletal remains (shells, algae, forams) Size of grains & types of fossils indicates environment Coquina – composed of shell fragments 2mm or larger; forms in high energy, shallow marine environment (beach) Fossil Limestone – any limestone containing fossils; may be fine grained or coarse grained; usually shallow marine Oolitic Limestone – formed from small spherical grains (oolites) with concentric layers; formed in very shallow marine, high energy intertidal environment or sometimes on lakebed by wave action. Right: enlarged view of modern oolites from the Bahamas Travertine Limestone formed from precipitation of calcite or aragonite in springs or caverns Often appears as layers of crystals It is a chemical/crystalline form of limestone Often used as building material Hand sample of travertine showing crystalline layers Travertine terraces at Mammoth Hot Springs, Wyoming Stalactites in a cave are composed of travertine Chalk & Diatomite Chalk and Diatomite are organic sedimentary rocks composed of the shells of microscopic one celled photosynthetic protists Both rocks are light colored and powdery Chalk is a type of limestone, formed from forams and coccoliths Chalk is composed of calcite and will bubble with acid Diatomite is composed of the remains of diatoms Chalk is composed of coccoliths (microscope view on right) Diatom skeletons are composed of opal (silica); diatomite is less dense than chalk and will not bubble with acid Chalk formed in moderately deep marine environments Diatomite formed in lake or marine environments Diatomite is composed of diatoms (microscopic view on right) Chemical Sedimentary Rocks Crystalline rocks composed of one mineral Rock salt (Halite) and Gypsum form by the evaporation of water (usually seawater) and the precipitation of dissolved minerals. Chemical sedimentary rocks that form by the evaporation of water are called evaporites. Rock Salt (Halite) Rock Gypsum (alabaster) Geology students walking on evaporitic deposit of salt in western US Chemical Sedimentary Rocks : Chert & Dolostone Chert is a fine grained silica rich microcrystalline sedimentary rock. It is composed of quartz (SiO2). It often occurs as nodules in limestone or chalk where it is believed to be a replacement mineral. It occurs in layers as a primary deposit in some areas. The banded iron formations of Precambrian age are composed of alternating layers of red chert (jasper) with hematite. Chert comes in many colors, and the dark grey to black form is often called flint. Chert specimens showing different color varieties. Top right: flint nodule in chalk. Left: Banded iron with red chert (jasper) and iron oxide Dolostone is composed of the mineral dolomite and is often described as a “non-descript” rock; looks like driveway gravel. Most dolostone formed when magnesium replaced calcium in limestone or lime mud before lithification. Often has vugs with dolomite crystals Dolostone – looks fine grained and non-descript. Right: vug in dolostone with dolomite crystals. Sedimentary Environments Rock Type, Fossils, & Sedimentary Structures Help Indicate Environment Metamorphic Rocks Metamorphic rocks form when preexisting rocks (igneous, sedimentary, or metamorphic) are exposed to high temperatures and pressures under the Earth's surface. The word metamorphic means "changed form.” Metamorphic rocks can form from sedimentary, igneous, or metamorphic rocks Metamorphism causes changes in the texture and mineralogy of other rocks. Metamorphism results from: 1. High temperatures, 2. High pressures, and 3. Chemical reactions Metamorphic Rock Classification Metamorphic Textures: Foliated • Mineral grains are aligned perpendicular to pressure • Ranges from low grade with microscopic grains (slate) to high grade with large banding Nonfoliated Marble Quartzite Composition: calcite Composition: quartz Origin: metamorphism of limestone Origin: metamorphism of sandstone Identification: acid test; softer than glass Identification: harder than glass Grade of Metamorphism Slate Phyllite Garnet Mica Schist Gneiss Low Grade ------------------------Medium Grade --------------------High Grade Grade of Metamorphism Grade of metamorphism depends on depth and pressure Types of Metamorphism Contact metamorphism Alteration of rock by heat adjacent to hot molten lava or magma. Economically important as setting for metallic ores – gold, silver, copper, lead, zinc, etc. Regional metamorphism large scale; associated with mountain building Grade increases with increasing depth and pressure Rocks are foliated (minerals are aligned perpendicular to pressure) Metamorphism - occurs with mountain building due to plate collisions Regional metamorphism often results in deformation Contact Metamorphism Igneous Intrusions cause contact metamorphism Metamorphic Minerals Common Metamorphic Minerals Some pre-existing minerals, unstable at the higher temperature and pressure conditions, transform into new minerals. Others recrystallize and grow larger. Metamorphic rocks tend to be dominated by minerals you already know: feldspar, quartz, muscovite, biotite, amphibole, and calcite/dolomite. However, a few minerals are found exclusively or mainly in metamorphic rocks: Garnet – most common in metamorphic rocks; some in igneous rocks. Almandine is found in schist, gneiss, and pegmatites. Staurolite – indicates intermediate to high grade regional metamorphism Kyanite - formed from high pressure metamorphism of clay minerals; found in gneisses and schists Tremolite – forms from metamorphism of sediments rich in dolomite and quartz Talc – forms from metamorphism of magnesian minerals such as serpentine, olivine, pyroxene, amphibole in the presence of carbon dioxide and water. Wollastonite – forms from thermal metamorphism of impure limestone or dolostone