MINERALS & ROCKS OF IOWA

Transcription

1 MINERALS & ROCKS OF IOWA Geologic Resources of Iowa University of Northern Iowa & the Iowa Limestone Producers Association

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3 MINERALS

4 SILICA TETRAHDRONS

5 MINERAL IDENTIFICATION Minerals are identified by their physical and chemical properties

6 Non-Metallic LUSTER Metallic

7 COLOR

8 CRYSTAL FORM

9 BREAKAGE / CLEAVAGE

10 HARDNESS

11 STREAK

12 THE PHYSICAL PROPERTIES OF MINERALS Luster (Metallic OR Non-Metallic) Color Breakage / Cleavage Hardness Specific Gravity Streak Other

13 OTHER Magnetic React with Hydrochloric Acid (HCL) Taste Smell Optical

14 ROCKS Are heterogeneous Made up of multiple minerals AND/OR other rocks

15 ROCK CYCLE

16 THE EARTH S CRUST IGNEOU S

17 IGNEOUS

18 EXTRUSIVE VERSUS INTRUSIVE

19 IGNEOUS ROCKS

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21 CONTINENTAL VERSUS OCEANIC CRUST

22 ROCK CYCLE

23 SEDIMENTARY ROCKS CLASTIC CHEMICAL

24 SEDIMENTARY TEXTURE or PARTICAL

25 SEDIMENTARY COLOR SORTING

26 SEDIMENTARY

27 SEDIMENTARY

28 ROCK CYCLE

29 Low Grade Shale Slate Phyllite Schist Gneiss METAMORPHIC

30 METAMORP HIC

31 MINERALS & ROCKS OF IOWA

32 GEOLOGIC RESOURCES OF IOWA The Earth s naturally occurring products of geologic, biologic, and/or chemical processes that are useful to society and economically feasible to extract (?Short-term versus long-term?)

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34 LOCAL MINERALS

35 GYPSUM Chemical formula = CaSO4. 2H2O Luster- Non-Metallic (vitreous, silky) Color White to clear Breakage 1 perfect platy 2 others Streak - White

36 GYPSUM S BIA GRAPHY Name Gypsos, Greek for plaster Source Webster, Des Moines, and Marion Counties Use plaster, drywall, cement Economy Approx. 2 million tons mined from Iowa per year ($11 million)

37 GALENA Chemical formula PbS Luster = Metallic Color Grey, silver Breakage Cubic Streak grey

38 GALENA S BIA GRAPHY Name Galena, Latin for lead-ore Source Dubuque, IA Galena, IL Use lead ore bullets, transistors Economy Peak (1845 to 1855) around 4000 tons per year

39 PYRITE Chemical formula FeS2 Luster = Metallic Color Yellow, brass Breakage none/fracture Streak yellowish grey Hardness 4 (penny to nail)

40 PYRITE S BIA GRAPHY Name Pyrite, Greek pyr for fire Source minor amounts in limestone Use Sulfur, sulfuric acid Economy not economically feasible in Iowa, not concentrated

41 CALCITE Chemical formula CaCO3 Luster = Non Metallic Color Yellow, clear, red, brown Breakage 3 perfect planes 90 Streak white Hardness = 3 (fingernail to penny)

42 CALCITE S BIA GRAPHY Name Chalx Greek for lime Source primary mineral of limestone, pure crystals are not common.. Use to help make steel, cement, and glass Economy not as a mineral, only as aggregate

43 QUARTZ Chemical formula SiO2 Luster = Non Metallic Color clear, white, rose, smokey Breakage None / fracture Streak none Hardness = 7 (glass)

44 QUARTZ S BIA GRAPHY Name Quarz, German? Source Igneous rocks, In Iowa as silicate sand Use foundry, glass, and chemical industries Economy exploding as fracking sand

45 LOCAL ROCKS Rocks are aggregates of more than one mineral and or other rocks Rocks are heterogeneous

46 LIMESTONE Majority of Iowa s bedrock Major source of aggregate Major types Crystalline Fossiliferous Micrite / Lithographic Oolitic

47 WHAT S LIMESTONE ANYWAY? Limestone = a biochemical sedimentary rock made up mostly of calcium carbonate Mineral Crystal system Formula Remarks Calcite Rhombohedral CaCO3 Dominant limestone mineral, especially in rocks older than Cenozoic Aragonite Orthorhombic CaCO3 Dominant mineral in Recent carbonate sediments; alters readily to calcite

48 HOW DO LIMESTONES FORM? Most limestones are simply the cemented remains of marine shells Limestone anatomy Grains Skeletal particles, ooids, peloids Lime mud Microscopic crystals produced by calcareous algae and through abrasion of larger particles Cement Inorganically precipitated CaCO3 crystals

49 OOIDS

50 PELOIDS

51 SKELETAL GRAINS

52 LIME MUD

53 CALCITE CEMENT

54 FACTORS AFFECTING PRECIPITATION OF CACO3 IN SEA WATER Factor Type of change Physical effect Effect on CaCO3 Temperature Increase Loss of CO2, increase in ph I ncrease precipitation Pressure Decrease Loss of CO2, increase in ph I ncrease precipitation Salinity Decrease Decrease activity of foreign cations I ncrease precipitation Photosynthesis Removes CO2 from sea water; ph increases I ncrease precipitation Bacterial activity Catalyzes CaCO3 precipitation I ncrease precipitation

55 WHERE DO LIMESTONES FORM? Because CaCO3 precipitates most readily in warm, well lit, agitated water of normal marine salinity most limestones form in shallow, tropical depositional environments e.g., Bahamas, central America, Persian Gulf, NW shelf of Australia, Great Barrier Reef, Malaysia, Indonesia, etc.

56 MODERN CACO3 DEPOSITIONAL ENVIRONMENTS Note: Although cool water carbonates Are forming in many places, they are highly prone to dissolution and therefore do not become major limestone accumulations *

57 CAICOS PLATFORM (BAHAMAS) Reef tract Quiet water high-energy ooid shoals Prevailing winds

58 IOWA DURING THE DEVONIAN PERIOD

59 CRINOIDS

60 DOLOSTONE Mg replaces Ca within CaCO3 May contain fossils Also used as aggregate, though typically not as much as limestone

61 SANDSTONE Quartz GREYWACKE Arkosic (feldspar) Lithic

62 SANDSTONE Quartz Arkosic (feldspar) Lithic

63 SHALE Silt to clay sized particles Mixed assemblage of minerals Deposited in low energy environments Ponds Floodplains

64 GEODE Latin Earthlike Geologic recourses of great beauty 1967, named the official state rock by the Iowa General Assembly Warsaw and Keokuk formations of SE Iowa, W. Illinois, and NE Missouri May also be found in NE Iowa near Jesup

65 HOW DO GEODES FORM? 1) Geode precursors were concretions (nodules formed by outward growth around some nucleus) which grew within soft, unlithified sediment. 2) The outer shells of these concretions were replaced subsequently by chalcedony. 3) The interiors of the concretions were dissolved, leaving a hollow space into which quartz and other crystals may grow. Brian J. Witzke

66 HOW DO GEODES FORM? 4) Minerals/crystals inside geodes were transported in groundwater (saturated) solutions and then precipitated as replacements of the geode walls or as crystalline growths within their hollow interiors. 5) The ultimate source of the mineralizing waters remains speculative. 6) Many common geode mineral, especially quartz, are weakly soluble. Therefore, substantial volumes of water had to migrate through the lower Warsaw strata to precipitate the observed minerals. Brian J. Witzke