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Earth’s Buried Treasures

Earth Science. Earth’s Buried Treasures. An Introduction to Earth Materials : Minerals. The Importance of Minerals. Definition of a Mineral. A Mineral is: Naturally Occurring Inorganic Solid Definite chemical composition Orderly internal arrangement of atom. Gemstones.

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Earth’s Buried Treasures

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  1. Earth Science Earth’sBuriedTreasures An Introduction to EarthMaterials: Minerals

  2. The Importance of Minerals

  3. Definition of a Mineral A Mineral is: • Naturally Occurring • Inorganic • Solid • Definite chemical composition • Orderly internal arrangement of atom Gemstones Mineraloidslack an internal arrangement of atoms

  4. Rocks vs. Minerals Minerals are the components of rocks. A thoroughunderstanding of mineralsprovide a betterunderstanding of the formation of rocks.

  5. Elements of the Earth’s Crust An element is a substance that cannot be broken down into simpler, stable substances by chemical means. Each element has physical and chemical properties that can be used to identify it. The diagram above shows common elements in Earth’s crust. Approximately 90 elements occur naturally on Earth. Eight of these make up more than 98%of Earth’scrust.

  6. Major Mineral Group: The Silicates Oxygen and Silicon are the most abundant elements in the Earth’s crust so… The Silicates are the most abundant group Made up of the Silicon-Oxygen Tetrahedron Identified by the SiO in the chemical formula Example: AlSiO2

  7. Other Mineral Groups To determine the mineral group, look at the last part of the chemical formula

  8. Other Mineral Groups

  9. MineralResources Earth’s crust contains useful mineral resources. The processes that formed many of these resources took millions of years. Many of these mineral resources are mined for human use. Mineral resources can be either metals, such as gold, Au, silver, Ag, and aluminum, Al, or nonmetals, such as sulfur, S, and quartz, SiO2. If a volume of rock isenrichedenough in an element or mineral to bepotentialvaluableitiscalled a mineraldeposit

  10. Mineral Environments of Formation Mineral Environments refers to the "geologic environments" in which minerals occur – the types of rocks in which they are found.  While some minerals occur in two or more environments, others tend to be restricted to a single environment.  Example: If you think you have found the mineral kyanite in a sedimentary sandstone and see that it is a mineral formed by metamorphic processes you’ll know it can’t be kyanite.  Try celestite…  If you think you have found topaz in a cavity in basalt and read that it is largely restricted to pegmatite you’ll know it isn’t topaz.  And so on. Chapter18.9

  11. Mineral Environments of Formation Ores form in a variety of ways, as shown below. Some ores, such as ores of chromium, Cr, nickel, Ni, and lead, Pb, form within cooling magma. As the magma cools, dense metallic minerals sink. As the minerals sink, layers of these minerals accumulate at the bottom of the magma chamber to form ore deposits. By knowing how specific minerals and the environments in which they form you can make an interpretation of paleo-environments as well as locate mineral resources. You can also use this to differentiate between similar appearing minerals

  12. Mineral Environments of Formation The environments of mineral formation and growth are highly varied, ranging from slow crystallization at the high temperatures and pressures of igneous melts deep within the Earth's crust to the low temperature precipitation from a saline brine at the Earth's surface. Various possible methods of mineral formation include: - sublimation from volcanic gases - deposition from aqueous solutions and hydrothermal brines - crystallization from an igneous magma or lava - recrystallizationdue to metamorphic processes and metasomatism - crystallization during diagenesis of sediments - formation by oxidation and weathering of rocks exposed to the atmosphere or within the soil environment.

  13. Mineral Environments of Formation 18.09.c Igneous crystallization Hydrothermal deposition Hydrothermal replacement Volcanism and volcanic pipes Metamorphism

  14. Mineral Environments of Formation Minerals Formed in Igneous Environments Quartz Na/Ca Feldspar K Feldspar Mica (Plagioclase) (Orthoclase) (Biotite) Mica Amphibole Pyroxene Olivine (Muscovite)

  15. Mineral Environments of Formation Minerals formed in Metamorphic Environments Quartz Na/Ca Feldspar K Feldspar Mica Mica (Plagioclase) (Orthoclase) (Biotite) (Muscovite) Serpentine Chlorite Garnet Calcite

  16. Important Base Metal Deposits Mineral Environments of Formation Ores Hematite (Iron) Galena (Lead) Bauxite (Aluminum) Bornite (Copper) Sphalerite (Zinc) Apatite (Phosphorous Used in Fertilizers)

  17. Mineral Environments of Formation Where do Platinumdepositsoccur? Most Platinumdeposits are associatedwithmafic or ultramaficigneou rocks that come from the mantle and rose into the crust. Picturedis the BushveldComplex in South Africa. The darklayers are platinum and chromite and the light layers are anorthosite.

  18. Mineral Environments of Formation Two Other Types of Metal Deposits Mississippi Valley lead-zinc deposits Sudbury nickel deposits Shatter cones (from impact) 18.11.d

  19. Mineral Environments of Formation How do precious metal deposits form? Veins from hot water Veins in metamorphic rocks Gold in gravel Gold-bearing conglomerates (placer deposits) By-product gold Low-grade gold deposits 18.10.a

  20. Mineral Environments of Formation Quartz Veinwith Gold Deposits

  21. Mineral Environments of Formation Diamond Formation Kimberliteis the type of rock typically associated diamonds Diamonds do not originate from the metamorphism of coal but rather form in the mantle and are brought to the surface by geologic features called kimberlite pipes

  22. Mineral Environments of Formation Other sources of diamond formation: Kimberlite Pipe (mostcommon) Subduction Zones Asteroid Impact Sites Meteorites(brought by meteorites)

  23. Rubies are a form of corundum, a rare mineral made up of densely packed aluminum and oxygen atoms, which are normally colorless. When other atoms are substituted for a few of the aluminum ones, bright hues emerge. Small amounts of chromium impart the deep red color of ruby, traces of titanium and iron produce the stunning blue of sapphire, and chromium and ferric iron create the delicate orange shades of the extremely rare and costly padparadscha. Mineral Environments of Formation

  24. Mineral Environments of Formation Where do Copper Deposits form? Porphyry copper deposits Massive sulfide deposits Sedimentary copper deposits 18.11.a

  25. Mineral Environments of Formation 18.09.c Weathering enrichment Formation by weathering Mechanical concentration Low-temperature precipitation

  26. Important Minerals Mineral Environments of Formation Minerals formed From Weathering Quartz Kaolinite Hematite Bauxite

  27. Mineral Environments of Formation Gold that has been liberated by weathering and erosiongetcarriedaway by streams and depositwithinplacer deposits

  28. Minerals as Indicators of Ancient Environments Where do base metaldepositsform? Most of ouriron ores are minedfrom formations calledbandediron formations (BIF’s) . Theseiron and quartz richlayers are an indication of the Great Oxygenatingeventthatoccurredduring the Precambrian 2 billion yearsago Otheriron ore depositsform as magma intrudesinto the crust and releases metalrichfluids

  29. Evaporites and Precipitants Mineral Environments of Formation Gypsum and Halite are examples of evaporites. These minerals from in low temperature aqueous environments. Calcite and Travertine are examples of precipitants. These minerals precipitate out of water under the correct environmental conditions.

  30. Marine evaporite deposits in the United States Minerals as Indicators of Ancient Environments Gypsum and Halite are evaporitesthatform by the evaporation of ocean water.Thusthesedepositsindicate the location of ancientseas

  31. Minerals as Indicators of Ancient Environments This image, taken by the Mars Exploration Rover Opportunity's panoramic camera, is an approximate true-color rendering of the "Berry Bowl," a rock in the "Eagle Crater" outcrop that contains pebble-like hematite spherules Marble-like hematite concretions litter the Navajo Sandstone surface in southern Utah's Grand Staircase-Escalante National Monument.

  32. Minerals as Indicators of Ancient Environments

  33. Conclusion Earth’sBuriedTreasures An Introduction to EarthMaterials: Minerals

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