Minerals and Rocks Environmental Learning Community CORC 1332 Sept 21, 2010
Outline Quiz More on minerals Twinkies Rocks
How can you identify one mineral from another?
Distinguishing One Mineral from Another Crystal form Cleavage No cleavage Luster Color 04.03.a
Tests to Help Identify Minerals Hardness Effervescence Streak Density Magnetism 04.03.b
What Controls a Crystal s Shape? Halite (NaCl) Internal structure of halite Sizes and packing of atoms 04.04.a
Orderly arrangement of atoms Crystal Lattice 04.04.b Repeating pattern
How Are Atoms Arranged in a Mineral? Observe some ways atoms are arranged in a mineral 04.04.c1-3 Cubic Tetrahedron Octahedron
Atomic Scale of Mineral Cleavage Brown atoms bonded with blue atoms into flat sheets (strong bonds) Sheets joined by long bonds between sheets (break along weakest bonds) Cleave into sheets 04.05.a
Bonds with Same Strength Mineral can break along three sets of planes without passing through an atom Mineral breaks through the lattice in nearly any direction so it will fracture 04.05.b
Observe the number of cleavage planes in this mineral 04.05.c
Observe the number and relative orientation of cleavage planes in this mineral 04.05.c
Observe the number and relative orientation of cleavage planes in this mineral 04.05.c
Periodic Table Letters are abbreviation for element 04.06.a1 # is atomic number (number of protons) Color represents type of element
Mineral families Geologist have identified approximately 4000 mineral species. Out of every kg of material in Earth s continental crust, only 12 elements are present in quantities greater than one gram: oxygen, silicon, aluminum, iron, calcium, magnesium, sodium, potassium, titanium, hydrogen, manganese, and phosphorus.
Major Classes of Rock-Forming Minerals Oxides Carbonates Halides Silicates 04.06.b4 Native minerals Sulfides Sulfates
Important Minerals Sulfides: contain sulfur Oxides: contain oxygen Metals Malleable, lustrous, conductors Iron, aluminum, copper Nonmetallic minerals Ore Rock with valuable mineral
Silicates
Nonsilicate Minerals: Carbonates Calcite Dolomite 04.09.a
Nonsilicate Minerals: Halides and Sulfates Halite (halide) Gypsum (sulfate) 04.09.a
Nonsilicate Minerals: Oxides Magnetite Hematite 04.09.a
Nonsilicate Minerals: Sulfides Pyrite Galena Copper sulfide 04.09.a
Some important minerals in soils Quartz Silicate Primary Minerals formed by cooling of molten rock Name Feldspar (orthoclase and plagioclase) Silicate Mica (muscovite and biotite) Silicate Dark minerals (e.g., hornblende) Silicate Properties SiO 2 ; hard; weathers very slowly; major component of sands Hard; weathers slowly or moderately to form clay; provides plant nutrients; minor component of sands Appears to glitter in rocks and sands; provides potassium; weathers to form clays Easily weather to form clay Source: Gardiner and Miller, 2008. Soils in Our Environment, 11 th ed., p. 6
Some important minerals in soils Secondary Minerals formed by precipitated or recrystallized from solutions that contained elements from the dissolution of other minerals. Name Carbonates (calcite and dolomite) Gypsum Sulfate Oxide clays (e.g., goethite and gibbsite) Silicate clays (montmorillonite, illite, vermiculite, kaolinite) Properties CaCO 3 and (Ca-Mg)CO 3 ; slowly soluble sources of plant nutrients; common in soils in arid regions CaSO 4-2H 2 O; soft; soluble materials common in soils of arid regions Hydrated (containing structural water) microscopic particles formed from iron and aluminum; common in tropical soils Microscopic particles formed mostly from silica and aluminum; common in soils of temperate climates Source: Gardiner and Miller, 2008. Soils in Our Environment, 11 th ed., p. 6
Minerals & Their Uses
Extracting Minerals Locate deposit Analyze mineral composition Mine for minerals: many different ways Process mineral Make product
Near the surface Less expensive Overburden removed Open-pit Dig quarry Iron, copper, gravel Surface Mining
Strip mining Surface Mining Dig trench to extract mineral Dig parallel trench Cover old trench with new overburden Spoil bank
Subsurface Mining Minerals deep in ground Less land disturbance More expensive More hazardous Shaft mine Direct vertical shaft Coal
Slope mine Subsurface Mining Slanting passage Ore hauled in cars
Processing Minerals Smelting Melt ore to separate impurities from desired mineral Blast furnace Slag disposed of
Mining & The Environment Disturbs land Land prone to erosion further damage Uses a lot of water Contaminated streams Acid-mine drainage
Impacts of Refining About 80% of mined ore made of impurities Tailings Waste left behind Left in piles Toxic
Impacts of Refining Smelting emits pollutants Acid precipitation Hazardous solid and liquid wastes A lot of energy required
Restoration of Mining Lands When mine no longer profitable Prevents further degradation Filling in and grading the area Planting vegetation Surface Mining Control & Reclamation Act of 1977 Lands mined for coal
Outline Quiz More on minerals Twinkies Rocks
What makes twinkies rise?
What do you think will happen with? Baking powder and water Baking soda and water Baking soda with vinegar Baking soda with vinegar
Leavenings Make baked goods like twinkies light and fluffy Rocks and minerals with phosphate, sodium and calcium Baking soda: sodium bicarbonate Baking powder: made from baking soda and phosphate acids
Trona: sodium rich mineral Chemistry: Na 3 (HCO 3 )(CO 3 ) - 2H 2 O, Hydrated Sodium Bicarbonate Carbonate http://www.galleries.com/minerals/carbonat/trona/trona.jpg
Lake Gosiute Trona deposits Formed during Eocene (over 50 million years ago) Mountain building period with lots of volcanic ash, organic matter, lake sediments, water, and heat Conditions right for the precipitation of trona over 6 million years
Trona Trona Sodium Carbonate (Soda Ash) Sodium Bicarbonate (Baking Soda) Other uses of trona: glass, detergents, making paper
Western phosphate field Marine sedimentary rocks Deposited about 265 million years ago over a period of about 10 million years Rocks consist primarily of organic carbon- and phosphate-rich mudstone, siltstone, phosphorite, carbonate, shale, and chert
Phosphate rock
Phosphate Refineries Create monocalcium phosphate and sodium acid pyrophosphate Mixed with sodium bicarbonate to make baking powder
Limestone calcium rich http://krisdedecker.typepad.com/photos/uncategorized/20 08/06/28/limestone_mine.gif http://images.icnetwork.co.uk/upl/birmmail/may2009/2/5/image-5-for-bidto-revive-dudley-s-limestone-mines-gallery-24284093.jpg
Outline Quiz More on minerals Twinkies Rocks
Key points for rock cycle Rocks are transformed into different types over time Igneous: cooling and solidification of molten, material magma Intrusive Extrusive Sedimentary: transportation and deposition of particles Many different sedimentary environments Organic and inorganic particles Metamorphic: formed from igneous and sedimentary rocks through pressure and heat
Igneous rock examples *BASALT Environment of formation = extrusive (volcanic) Texture = fine Grain size = less than 1 mm Color = dark Density = high Composition = mafic *GRANITE Environment of formation = intrusive (plutonic) Texture = coarse Grain size = 1 mm to 10mm Color = light Density = low Composition = felsic
Metamorphic rock examples *SCHIST Texture = foliated (mineral alignment) Grain size = fine to medium Type of metamorphism = Regional (platy mica crystals visible from metamorphism of clay or feldspar) Composition = mica, quartz, feldspar, amphibole, garnet *GNEISS Texture = foliated (banding) Grain size = medium to coarse Type of metamorphism = Regional (high-grade metamorphism, some mica changed to feldspar, segregated by mineral type into bands) Composition = mica, quartz, feldspar, amphibole, garnet, pyroxene
Sedimentary rock examples *SANDSTONE Texture = clastic (fragmental) Grain size = sand (0.2 to 0.006 cm) Comments = fine to coarse Composition = mostly quartz, feldspar, and clay minerals; may contain fragments of other rocks *LIMESTONE Texture = bioclastic Grain size = microscopic to coarse Comments = cemented shell fragments or precipitates of biologic origin Composition = calcite
Rocks and minerals Minerals Naturally occurring Inorganic Definite chemical composition Crystalline structure Physical characteristics Form in different pressure and heat environments Rocks Aggregates of minerals Differ in mineral composition and texture Texture: size, shape and distribution of particles in rocks