MINERALS What Is a Mineral? A mineral, by definition, must meet four criteria. It must: • be a naturally occurring substance • be a solid substance • have an internal crystal structure and • have been formed by inorganic processes (in other words, it cannot be formed by an organism). A rock, by comparison, is composed of one or more minerals, one or more pieces of rock material, and even organic material (such as coal). How We Identify Minerals Minerals are identified based on their physical properties. There are a number of physical properties that can be easily tested in the laboratory. The results can be compared with charts of minerals’ physical properties in order to identify an unknown mineral sample. Scientists use these physical properties to determine a mineral’s identity. 1. Hardness. A mineral’s hardness is determined by comparing the mineral to the known hardnesses of the minerals in the Moh’s Hardness Scale. From softest to hardest, the minerals on the Hardness Scale are as follows: 1=Talc, 2=Gypsum, 3=Calcite, 4=Fluorite, 5=Apatite, 6=Orthoclase Feldspar, 7=Quartz, 8=Topaz, 9=Corundum, 10=Diamond. An unknown mineral that is harder than fluorite but softer than apatite has a hardness between 4 and 5. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
2. Specific Gravity is a measure of the density of a mineral. The density is determined by comparing the mass of the mineral with the mass of an equal amount of water. 3. Streak is the color of a mineral when it is crushed to a powder. This is found by rubbing the specimen on a piece of unglazed porcelain. Minerals with a hardness greater than 7 do not leave a streak. 4. Cleavage is a description of how a mineral breaks on flat planes. For example, galena breaks into cubes (cubic cleavage). Fluorite breaks into diamond shapes (octahedral cleavage). 5. Fracture is a description of how a mineral breaks when it doesn’t naturally break into flat planes. Hackly, conchoidal (shell-shaped), earthy, and irregular are some of the fracture descriptions. 6. Color is sometimes used to help identify a mineral. This is helpful for some minerals. But other minerals occur in so many different colors that color ultimately is not the best physical property for identifying an unknown mineral. 7. Luster is a description of how light reflects off of a mineral. Some of the luster descriptions are metallic, glassy (also called vitreous), earthy, adamantine (diamond-like), greasy, and dull. 8. Crystal System. Every mineral forms specific crystal shapes. There are over 3,500 mineral species. All of these species belong to one of seven different crystal systems. The crystal systems are determined by the internal arrangement of the molecules in the mineral. There are also some interesting physical properties that are unique to some minerals. When weak hydrochloric acid is applied to calcite, a chemical reaction causes the specimen to fizz. Hematite always has a deep, blood red streak. Clear calcite breaks a single ray of light into two in a physical property called double refraction. Magnetite and lodestone are magnetic. Lesson Checkpoint: How many different mineral species are there? © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
How Do Minerals Form? Minerals form in a wide variety of geologic environments. Some, like garnet, asbestos, talc, and kyanite, form as a result of intense heat and pressure present during the creation process of the mineral. GARNET Other minerals form from liquid rock (magma) as the magma cools. As the magma cools, ions in the magma combine to form specific minerals. In the early stages, minerals high in iron and magnesium form (like olivine). As the magma is depleted of iron and magnesium, minerals that are higher and higher in silica content form, like tourmaline, topaz and, finally, quartz. Amethyst Yet another group of minerals form as ocean water evaporates. As the water evaporates, the concentration of dissolved minerals gets higher and higher until the minerals start to precipitate and crystallize out of the ocean water. The most common mineral to form this way is halite (rock salt). Another precipitate mineral, as these are called, is gypsum. Lesson Checkpoint: What is the mineral name for rock salt? © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
Our Mineral Resources Very few minerals are mined and used as they are. Nearly all mineral resources need to be processed to one degree or another. Rarely, some deposits can be used as is. The native copper found in Michigan’s Upper Peninsula can be used with very little processing, for example. By comparison, the massive copper ore deposits of Arizona must be processed to remove the copper from the copper minerals. The concentration of the desired element or material in an ore deposit can determine whether the deposit is useful or not. Usually it is the value or price of the desired mineral that determines whether or not it is worth it for a company to mine the mineral. If the price of silver rises, silver ore with lower concentrations of silver can be mined for a profit. If the price is low, however, a company could lose money mining the silver ore. In most cases, the reserves of mineral materials in the Earth are sufficient to supply our needs. There is little to no danger of running out of quartz to make glass and computer chips or sulfur to make sulfuric acid. The more significant issues about mining and processing ores are environmental. Mining, particularly strip mining of the surface rock in a region, can create serious environmental and pollution problems. Reclaiming the land, which includes bringing in new topsoil and planting trees, grasses and other native plants, is a top priority of the mining industry today. Also, In addition, in many cases it is proving to be more efficient to recycle previously used materials rather than producing them from raw ores. For example, there are now companies that strip old computers of gold used in the electronics components. Renewable resources are increasingly important as the world’s nations consume larger and larger quantities of all commodities. How Are Minerals Used? It is said that if a resource is not grown, it is mined. Many of the commodities we consume every day are mined from rocks and minerals. Many are physically processed to be useful. For instance, gypsum is used to make wallboard for buildings. It is cleaned and processed into plaster that is then formed into the wallboards. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
On the other hand, many minerals are chemically processed for desired elements or compounds within the mineral. For example, the element fluorine found in the mineral fluorite is removed and combined with other compounds to make fluoride for toothpaste. Zinc is chemically removed from the mineral zincite. Copper is removed from a variety of copper ore minerals including malachite and cuprite. Lead is removed from galena. Sulfur is sometimes mined as a pure element, but more often it is removed from sulfide minerals like pyrite (“Fool’s Gold”). Minerals in Our World If you were to walk around your home, you would quickly discover a long list of minerals and materials from minerals that are used to make various items in your home. Here is a list of some of those materials. • Copper pipes and wires come from the copper minerals malachite and cuprite. • The steel used to make stoves, refrigerators, furniture and cars is a mixture of iron and other metals to make it strong. The iron comes from hematite and magnetite. • Glass windows and drinking glasses are made from quartz sand which is melted and mixed with other materials to give the glass its desired properties. • Gold is used in computers, cell phones and other electronic equipment because electrical connections made from gold conduct electricity extremely well and do not corrode. • Items made out of aluminum, like pots and pans, come from the mineral bauxite. • Table salt is the mineral halite. • The paint on the walls contains many minerals including talc, hematite, magnetite, mica, kaolin, and barite. • A television set alone contains about 35 different minerals and mineral products including quartz (for glass and for silicon for computer chips), copper (wire), gold (electrical connections and circuit boards), and the elements strontium and yttrium (from the minerals strontianite and the rare mineral gadolinite, respectively). © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
This is only a small list of the minerals around you every day in your home. Even more minerals are consumed by industry to make the products you use at home, at school, and at work. Sulfur is one of the most important industrial minerals. It is used to make rubber for tires and to make sulfuric acid. Sulfuric acid is important in many manufacturing processes. Sulfur is also used in making paper, fertilizer, plastics, drugs, and insecticides. Fluorite is used as a flux when making steel. A flux is a substance that lowers the melting point of another substance. Steel is made from iron and other metals to make cars, buildings, bridges, and machinery. Galena is the most important source of lead which is used to make batteries and solder. Feldspar is used to make ceramics and electrical insulators, and is used in the manufacture of glass, roofing materials, and some abrasives. Talc is used to make paint, ceramics, wall tile, and baby powder. As you can see, nearly every aspect of our lives relies in some measure on minerals and the elements found in minerals. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.