MINERALS ARE THE BASIS FOR MODERN SOCIETY Per capita use of minerals amounts to several thousand pounds. Much of your house is mined from the Earth. After “Out of the Rock” by the National Energy Foundation INDUSTRIAL MINERALS AROUND THE HOUSE Minerals are used around the house in many common products. ITEM MINERALS NEEDED TO PRODUCE THEM Carpet Calcium carbonate Glass/Ceramics Silica sand, limestone, talc, lithium, borates, soda ash, feldspar Vinyl Flooring Calcium carbonate, clay, wollastonite Glossy Paper Kaolin clay, limestone, sodium sulfate, lime, soda ash, titanium dioxide Cake/Bread Gypsum, phosphates Plant Fertilizers Potash, phosphates, nitrogen, sulfur Toothpaste Calcium carbonate, sodium carbonate, fluorine Lipstick Calcium carbonate, talc Baby Powder Talc INDUSTRIAL MINERALS AROUND THE HOUSE (continued) ITEM MINERALS NEEDED TO PRODUCE THEM Hair Cream Calcium carbonate Counter tops Titanium dioxide, calcium carbonate, aluminum hydrate Household Cleaners Silica, pumice, diatomite, feldspar, limestone Caulking Calcium carbonate, gypsum Jewelry Precious and semiprecious stones Kitty Litter Attapulgite, montmorillonite, zeolites, diatomite, pumice, volcanic ash Fiberglass Roofing Silica, borates, limestone, soda ash, feldspar Potting Soil Vermiculite, perlite, gypsum, zeolites, peat Paint Titanium dioxide, kaolin clays, calcium carbonate, mica, talc, silica Minerals are also used at your school. After “Out of the Rock” by the National Energy Foundation Minerals are in your teeth, bones, and even kidney stones. Specimen courtesy of D. Cook, Indiana University Department of Anthropology All minerals are made of naturally occurring elements. ELEMENTS AND MINERALS collection of unit cells crystal mineral unit cell atoms molecule This diagram shows the relationships between atoms: atoms form molecules which come together in minerals as a collection of unit cells. Unit cells form minerals and visible crystal forms. After Mineralogy, 1998, Dexter Perkins STRUCTURE Diamond Graphite Hard, bright, gem Soft, gray, lubricant The arrangement of atoms is important. The element carbon (C) can form diamond -- a hard, clear mineral -- or graphite -- a soft, gray mineral -- depending on the crystal structure. DEFINITION of MINERALS and ROCKS A naturally occurring, generally inorganic Mineral: solid that has an ordered arrangement of atoms and specific chemical and physical properties. 1. Naturally occurring: Not man-made (but there are synthetic “gems”) 2. Solid: Hard; not liquid or gas 3. Ordered arrangement of atoms: Made of atoms that are arranged in three dimensions; crystalline Is made of one or more minerals, usually Rock: occurring in large masses. ROCK CYCLE TYPICAL ROCK TEXTURES IGNEOUS SEDIMENTARY METAMORPHIC Crystalline Fragmental Foliated (interlocking) (clastic) (banded) IDENTIFYING MINERALS Properties used by geologists Shape: Symmetry, form, habit, twinning Cleavage: Tendency to break along the rows of atoms; shiny, flat fractures Hardness: Resistance to scratching Mohs Hardness Scale (from softest to hardest) 1. Talc 6. Feldspar 2. Gypsum 7. Quartz 3. Calcite 8. Topaz 4. Fluorite 9. Corundum 5. Apatite 10. Diamond Density: Weight (relative to equal volume of water) Appearance: Transparency, color, luster, fracture Streak: Color of the fine powder from a mineral Special Properties: 1. Magnetism 4. Chemical reactions 2. Optical properties 5. Action in heat/flame 3. Electrical properties 6. Taste One way to help identify rocks is to use a “scratch hardness test.” The items listed on the right side will make a visible scratch on any of the minerals listed above them. MOST COMMON INDIANA MINERALS ANHYDRITE GALENA APATITE * GYPSUM ARAGONITE LIMONITE BARITE MARCASITE CALCITE MELANTERITE CELESTITE MILLERITE CLAYS * PYRITE DOLOMITE QUARTZ * EPSOMITE SIDERITE FLUORITE SPHALERITE * Several varieties The most common Indiana mineral is calcite or calcium carbonate (CaCO3). Crystal structure of calcite. When allowed to freely grow into open spaces minerals can form beautiful geometric solids called crystals. CALCITE rhombohedral cleavage fragment Calcite is calcium carbonate. It fizzes in acid. It is usually white or colorless, but can be other colors because of impurities in it. It may have many outward shapes, but always breaks into little pieces shaped like rhombo- hedrons. Calcite makes up the rock called LIMESTONE. Limestone is used as fertilizer, aggregate, building stones, and to make cement. Crystals of calcite with trigonal pyramids. A vug (open space in rock) with iridescent calcite crystals in a limestone rock. Calcite crystals can also be found in geodes. A related mineral with the same chemistry as calcite but a different crystal structure is aragonite which forms white, needle-like crystals. Indiana limestone dissolves in acidic groundwater. These solution features are often seen in dimension limestone quarries. Indiana has many cave formations in limestone rock, called speleothems. Speleothems are made of calcite or aragonite. DOLOMITE Curved faces Pearly luster Dolomite is calcite with magnesium added. It fizzes in warm acid. It is usually pink or white and has curved faces. It is a common mineral and is used for building stones and for making heat-resistant bricks for furnace linings. Example of dolomite in pink crystals with purple fluorite crystals. FLUORITE Cubic crystals Octahedral cleavage Often zoned Fluorite is calcium fluoride (CaF2). It will change color under fluorescent light; this property is called fluorescence. It is usually purple, light green, yellow, or clear. It forms in cubes, but cleaves into octohedrons. It is used for a flux in smelting iron, for decorative stones, in the chemical industry, and for making optical equipment. Yellow fluorite with white calcite Calcite Fluorite This is a sample of a rare, fibrous form of fluorite. White gypsum and purple fluorite The mineral siderite (FeCO3) forms concretions. This one also contains white clay minerals. Magnified image of quartz geode containing a barite (BaSO4) crystal. Delicate blue celestite (SrSO4) crystals Crystals display special features inside. Here, a pointy, white phantom crystal is inside the clear calcite. Petroleum is included in this calcite crystal giving it a brown color. This calcite sample has inclusions of a dark sulfide mineral, marcasite. Chert, a very fine-grained variety of quartz (SiO2), was used extensively by Native Americans. chert spear point Crystals of quartz are common in geodes. This is a geode cut in two. The outside of geodes are bumpy and have spherical forms. This is a typical geode in the limestone bedrock. PYRITE Brassy yellow Dark tarnish Pyrite (FeS2) is iron sulfide. It is also called “fool’s gold” because it is a metallic golden color. Harder than gold, sparks will fly if it is hit with a hammer. It forms in cubes, and is not valuable by itself. Fossils are often replaced by pyrite. Pyrite is the most common sulfide mineral in Indiana. This pyrite nodule occurs in a black oil shale. Good crystals of pyrite are common. More typical occurrences of pyrite are in crystalline groups like these. This sample shows pyrite in limestone. Marcasite is also iron sulfide, but forms in a different crystal form as a pseudomorph of pyrite. The brown mineral sphalerite (ZnS) forms very large crystals in some cases. This crystal is about one foot long. Sphalerite also occurs in bands. Here, sphalerite and pyrite form the bands. The shiny, cubic mineral galena (PbS) is rare in Indiana. The rare mineral millerite (NiS) is the spidery, dark crystal growing upon quartz in this geode. Iron oxide such as this was used for red pigment by Native Americans. Small crystals of resistant, so-called “heavy minerals,” including gold (Au), can be concentrated from stream sediments. These minerals were brought to Indiana by glaciers. The calcite crystal pictured here is from Indiana. The journal Rocks and Minerals featured Indiana minerals in this 1986 issue. Contact: Indiana Geological Survey An institute of Indiana University https://IGWS.indiana.edu [email protected] (812) 855-7636.