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) Minerals Native Elements 31. Hematite Silicates Garnet group 16. Copper 35. Magnetite 6. Augite 2. Almandine 18. Diamond 10. Beryl 25. Gold Carbonates, Borates 20. Epidote Mica Group 26. Graphite 5. Aragonite 32. Hornblende 11. Biotite 50. Silver 7. Azurite 33. Kaolinite 34. Lepidolite 54. Sulfur 13. Calcite 38. Olivine 37. Muscovite 19. Dolomite 39. Opal Sulfides 36. Malachite 49. Rhodonite Quartz varieties 12. Bornite 59. Ulexite 51. Sodalite 41. Agate/Onyx 15. Chalcopyrite 53. Staurolite 42. Amethyst 23. Galena Phosphates, Sulfates 55. Talc 43. Chalcedony 40. Pyrite 4. Apatite 56. Topaz 44. Citrine 52. Sphalerite 9. Barite 57. Tourmaline 45. Crystal 14. Celestite 58. Tremolite 46. Jasper Halides 47. Milky Quartz 22. Fluorite Gypsum varieties: Feldspar - Plagioclase 48. Rose Quartz 30. Halite 27. Alabaster Series 1. Albite 28. Satin Spar *Specimen numbers are the Oxides / Hydroxides 29. Selenite Feldspar – potassium same as in previous and feldspar current Science Olympiad 8. Bauxite Rock and Mineral Kits that 3. Microcline may be ordered from Wards 17. Corundum [Amazonite] Science Olympiad Kits. 24. Goethite/ 21. Orthoclase Limonite Additional Minerals (Nationals only)
Actinolite Kyanite Labradorite [plagioclase feldspar series] Pyrolusite Rhodochrosite Labradorite feldspar Rutile Zircon Spodumene Stilbite Turquoise Zircon
Kyanite Rhodochrosite Rocks Sedimentary (cont)
Metamorphic Coal Varieties: 77. Anthracite 60. Gneiss 79. Bituminous 61. Marble 86. Lignite 62. Phyllite Igneous 63. Quartzite 82. Conglomerate 64. Schist [Garnet] 67. Andesite 84. Diatomite 65. Schist [Mica] 68. Basalt 85. Dolomite Rock or Dolostone 66. Slate 69. Diorite 86. Lignite Coal 70. Gabbro 71. Granite Limestone varieties: 72. Obsidian 87. Chalk 73. Pegmatite 83. Coquina 74. Pumice 89. Fossiliferous limestone 75. Rhyolite 90. Oolitic limestone 76. Scoria 91. Travertine
Sedimentary 92. Sandstone 93. Shale 78. Arkose 80. Breccia 81. Chert 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 C. Tourmaline D. Olivine E. Apatite
2. Identify Mineral B. A. Hornblende B. Augite C. Apatite D. Tourmaline 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? Sample B A.Fine quality crystals are cut into faceted semi-precious gems. (Tourmaline) 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. 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? Sample A (Obsidian) A.Gabbro C. Diorite B.Granite D. Andesite
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 Pyrite Sulfur
Gold Malachite Copper Color - tourmaline Color may be helpful but other properties are needed because: The same mineral has many color varieties Color
Different minerals have the Halite same color Calcite or are colorless!
Selenite Gypsum 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) Two Directions (Feldspar) Rhombohedral (Calcite)
Cubic (Galena) Octohedral (Fluorite) Types of Fracture -breaks in random directions (no planes of weakness)
Conchoidal (shell Fibrous (narrow splinters) - asbestos like) - Quartz
Uneven - Kaolinite Hackly (jagged edges) - Copper 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 Identifying crystal systems will NOT indicate the crystal system for be required in New York each mineral based on their competitions except for isometric research and their notes. (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 Oxides – combination of a metal & of a single element. Ex. copper, gold, oxygen, common ore minerals. Ex. graphite, sulfur, silver Hematite (Fe), corundum (Al)
Silicates - made from metals Sulfides: compounds of a metal combined with silicon and oxygen; with sulfur, common ore minerals. largest group of minerals; silicon Ex. Galena (Pb), Sphalerite (Zn), tetrahedron structure, most Pyrite (Fe), Chalcopyrite & Bornite common mineral family, many (Cu, Fe) subgroups; some are very complex. Ex. Quartz, feldspars, micas, olivine, hornblende, tourmaline, garnets, augite, talc, epidote, etc. Mineral Classification – cont.
Sulfates : compounds of sulfur with Phosphates: contain PO4 ; not metals and oxygen; contain SO4 ; as common. Ex. Apatite often form in evaporite environments. Ex. Gypsum Halides – form from halogen (calcium), barite (barium), celestite elements (chlorine, fluorine) with (strontium) metallic elements. Usually very soft and easily dissolved in water. Carbonates – minerals made of Ex. Halite (NaCl) and fluorite. carbon, oxygen, and a metallic
element (contain CO3); most fiz in acid. Ex. Calcite, dolomite, malachite. 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
Pumice has glassy texture Obsidian showing glassy but often doesn’t look like Fine grained texture glass due to holes from gases (Aphanitic) – crystals or grains smaller than 1 mm; cools relatively fast from lava ex. Basalt, rhyolite, andesite
Basalt magnified 30 x under Basalt with illustrating uniform microscope showing fine appearance of fine grained texture 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 Dikes cutting across existing rocks Sill
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, Breccia – angular Conglomerate – rounded beaches, lakes fragments; mixed pebble fragments; mixed pebble Rock type depends on grain size size and smaller size and smaller Fossils may be present, particularly in shale and sandstone
Sandstone – sand Shale – clay sized sized; mostly quartz 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, Coquina – composed of shell Fossil Limestone – any limestone forams) fragments 2mm or larger; forms containing fossils; may be fine grained in high energy, shallow marine or coarse grained; usually shallow Size of grains & environment (beach) marine types of fossils indicates environment
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, Stalactites in a cave are composed of travertine Wyoming 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 Chalk is composed of coccoliths (microscope view on right) Diatomite is composed of the remains of diatoms 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 Rock Salt (Halite) are called evaporites.
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 specimens showing composed of alternating layers of red Chert different color varieties. Top chert (jasper) with hematite. right: flint nodule in chalk. Chert comes in many colors, and the Left: Banded iron with red dark grey to black form is often called chert (jasper) and iron oxide flint. 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. Dolostone – looks fine grained and non-descript. Often has vugs with dolomite crystals Right: vug in dolostone with dolomite crystals. Sedimentary Environments Rock Type, Fossils, & Sedimentary Structures Help Indicate Environment Metamorphic Rocks Metamorphic rocks form when pre- existing 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 Origin: metamorphism of limestone sandstone Identification: acid test; Identification: harder than softer than glass 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