5Rocks vs. MineralsWhile two samples of the same type of rock may vary greatly in the amounts of different minerals they contain, minerals are always:Made of the same materials in the same proportions.Therefore, a ruby found in India has the same makeup as a ruby found in Australia. A mineral is the building block of rocks.
6Minerals Form In Nature Minerals are formed by natural processes. Every type of mineral can form in nature by processes that do not involve living organisms. A few minerals can also be produced by organisms as part of their shells or bones.Rocks are different from minerals in that rocks only have two of the four characteristics listed on the last slide.Rocks are a solidAnd rocks form naturally
7Mineral FormationMinerals form in many ways. The mineral halite, which is used as table salt, forms when water evaporates in a hot, shallow part of the ocean, leaving behind the salt it contained. Many types of minerals, including the ones in granite, develop when molten rock cools. Talc, a mineral that can be used to make baby powder, forms deep in Earth as high pressure and temperature cause changes in solid rock.
8Minerals are SolidA mineral is a solid—that is, it has a definite volume and a rigid shape. Volume refers to the amount of space an object takes up. For example, a golf ball has a smaller volume than a baseball, and a baseball has a smaller volume than a basketball. A substance that is a liquid or a gas is not a mineral. However, in some cases its solid form is a mineral. For instance, liquid water is not a mineral, but ice is.
9Minerals have a definite Chemical makeup!!!!! Each mineral has a definite chemical makeup: it consists of a specific combination of atoms of certain elements. An element is a substance that contains only one type of atom. In turn, an atom is the smallest particle an element can be divided into.
10Chemical Makeup Continued Everything you can see or touch is made up of atoms. Some substances, including the minerals gold and copper, consist of just one element. All the atoms in gold or copper are of the same type. However, most substances contain atoms of more than one element. Most minerals are compounds, substances consisting of several elements in specific proportions. Halite, for example, has one atom of sodium for every atom of chlorine. The types of atoms that make up a mineral are part of what makes the mineral unique. The way in which the atoms are bonded, or joined together, is also important. As you will read, many properties of minerals are related to how strong or weak the bonds are.
12Crystal StructureIf you look closely at the particles of ice that make up frost, you will notice that they have smooth, flat surfaces. These flat surfaces form because of the arrangement of atoms in the ice, which is a mineral. Such an internal arrangement is a characteristic of minerals. It is the structure of a crystal, a solid in which the atoms are arranged in an orderly, repeating three-dimensional pattern.
13Crystal StructureEach mineral has its own type of crystal structure. In some cases, two minerals have the same chemical composition but different crystal structures. For example, both diamond and graphite consist of just one element—carbon. But the arrangements of the carbon atoms in these two minerals are not the same, so they have different crystal structures and very different properties. Diamonds are extremely hard and have a brilliant sparkle. Graphite is soft, gray, and dull.
14Crystal StructureEach mineral has its own type of crystal structure. In some cases, two minerals have the same chemical composition but different crystal structures. For example, both diamond and graphite consist of just one element—carbon. But the arrangements of the carbon atoms in these two minerals are not the same, so they have different crystal structures and very different properties. Diamonds are extremely hard and have a brilliant sparkle. Graphite is soft, gray, and dull.
15Crystals Continued In nature, a perfect crystal is rare. One can grow only when a mineral is free to form in an open space—a condition that rarely exists within Earth's crust. The photographs on page 47 show examples of nearly perfect crystals.
17Minerals are grouped according to composition. Scientists classify minerals into groups on the basis of their composition. The most common group is the silicates. All the minerals in this group contain oxygen and silicon—the two most common elements in Earth's crust—joined together.
18Mineral CompositionThough there are about 3800 different minerals, only about 30 are common in Earth's crust. These 30 minerals make up most rocks in the crust. For that reason, they are called rock-forming minerals. Silicates, which make up about 90 percent of the rocks in Earth's crust, are the most common rock-forming minerals. Quartz, feldspar, and mica (MY-kuh) are common silicates.
20Mineral CompositionThe second most common group of rock-forming minerals is the carbonates. All the minerals in this group contain carbon and oxygen joined together. Calcite (KAL-SYT), which is common in seashells, is a carbonate mineral.
21What Will you Learn in Section 2.2 Which mineral properties are most important in identification?How minerals are identified by their properties?
22What can you tell by looking at a mineral? The photographs at the right show five pieces of the mineral fluorite. As you can see, the pieces are very different in color and size. Fluorite occurs in many colors, even in colorless forms. Its crystals can be well formed or poorly formed. Also, the sides of the crystals may be smooth or rough.
23A mineral's appearance helps identify it. To identify a mineral, you need to observe its properties—characteristic features that identify it. You might begin by looking at the mineral's color. However, many minerals occur in more than one color, so you would need to examine other properties as well. You might also notice how the mineral reflects light, which determines how shiny or dull it is. Most minerals reflect light in characteristic ways. In this section you will read about how the properties of a mineral—including its appearance—are used to identify it.
24LusterA mineral's luster is the way in which light reflects from its surface.The two major types of luster are metallic and nonmetallic.
25LUSTERMetallic luster looks as if it were made of metal.
26LUSTERA mineral with a nonmetallic luster can be shiny, but it does not appear to be made of metal. Like a mineral's color, its luster may vary from sample to sample. If a mineral has been exposed to the atmosphere or to water, its surface luster can become dull.
27Lets Fill In The Chart On Luster ObjectPropertiesMetallicNonmetallicDrinking GlassGlassyPearlPearlyRayon ClothSilkyNailShiny, BrightQuarterShinyFaucet
28Challenge Which metals occur naturally in pure form in nature? Which metal do not occur naturally?Do you know of any metal that is not metallic?
29Directions for 2/4/10Today you will be conducting the first of several tests to determine the names of minerals.Today you will test Luster!!!Groups of four or five students!You will need activity sheet 3 on my desk, all students.
30Ways to Identify a Mineral LusterHardnessCleavageFracture Density Streak
31Hardness Hardness is another dependable clue to a mineral's identity. A mineral's hardness is its resistance to being scratched.A mineral's hardness is determined by its crystal structure and the strength of the bonds between its atoms. Harder minerals have stronger bonds.
32Mohs ScaleA scale known as the Mohs scale is often used to describe a mineral's hardness.This scale is based on the fact that a harder mineral will scratch a softer one.A mineral can be scratched only by other minerals that have the same hardness or are harder.
33When identifying the hardness of minerals ask yourself this When identifying the hardness of minerals ask yourself this. This mineral is only as hard as what? Your fingernail, the penny, the nail. Or can the mineral scratch the glass? If yes to glass than it’s hardness is 6-9. You will not have a 10 for this activity!!!!!!!!
34Hardness ContinuedIn place of minerals, you will use your fingernail, a copper penny, and a steel nail to test an unknown mineral. To avoid damage to the minerals, you can test whether the mineral scratches these items.
35Hardness TestPLEASE READ ALL THE DIRECTIONS FOR THE HANDOUT, AFTER I GO OVER IT IN CLASS!!!!!!!!!One person from each group will get all the supplies for this activity. That person will sign in and out for the group and will be responsible for all items!
36Ways to Identify a Mineral LusterHardnessStreakCleavageFracture Density
37Color and StreakSome minerals can be almost any color, but most minerals have a more limited color range. For example, a particular mineral may almost always be brown to black.
38Color and Streak Three main factors cause minerals to vary in color. 1. First, a mineral may get its color from tiny amounts of an element that is not part of its normal chemical makeup.For example, a sample of pure quartz is clear and colorless, but tiny amounts of iron can give quartz a violet color.
39Color and Streak2. Second, a mineral's color can change when it is at or near Earth's surface and is in contact with the atmosphere or water.3. Third, mineral crystals can have defects in their crystal structures that change their color.
40Streak Some minerals have a different color when they are ground into a fine powder than when they are left whole. A mineral's streak is the color of the powder left behind when the mineral is scraped across a surface.
41All samples of the same mineral have the same streak. Streak is a better clue to a mineral's identity than surface color is.All samples of the same mineral have the same streak.
42Streak vs. ColorWhat is the difference between color and streak?
44Today You Will Test Streak You will use a tile of unglazed porcelain, called a streak plate, as a tool to identify minerals by their streaks.PLEASE READ THE DIRECTIONS ON THE HANDOUT BEFORE YOU START!!!!!!!!!!!
45Minerals with special Properties Minerals in the carbonate group, such as calcite, react with acid. Chalk is a familiar item that is made up of carbonate minerals. The test consists of putting a drop of a weak solution of hydrochloric acid on a mineral sample. If the acid reacts with the mineral, carbon dioxide gas will form and bubble out of the acid. The bubbles show that the mineral is a carbonate.
46FluorescentSome minerals have a property known as fluorescence (flu-REHS-uhns). Fluorescent minerals glow when they are exposed to ultraviolet (UHL-truh-VY-uh-liht) light. The word fluorescence comes from the name of the mineral fluorite, which has this property.
47Magnetic MineralsA few minerals respond to magnets. A magnet is pulled toward these minerals. The mineral magnetite strongly attracts magnets, and some other minerals weakly attract magnets. To test a mineral, hold a magnet loosely and bring it close to the mineral. You will be able to notice if there is even a small pull of the magnet toward the mineral. Magnets are commonly used in laboratories and industries to separate magnetic minerals from other minerals.
48CleavageEach kind of mineral always breaks in the same way, and this property can help identify a mineral. In fact, the way a mineral breaks is a better clue to its identity than are its color and luster.
49CleavageCleavage: is the tendency of a mineral to break along flat surfaces.The way in which a mineral breaks depends on how its atoms are bonded, or joined together. In a mineral that displays cleavage, the bonds of the crystal structure are weaker in the directions in which the mineral breaks.
51Fracture: is the tendency of a mineral to break into irregular pieces. Some minerals such as quartz break into pieces with curved surfaces, as shown below. Other minerals may break differently—perhaps into splinters or into rough or jagged pieces.
52FractureIn a mineral that displays fracture, the bonds that join the atoms are fairly equal in strength in all directions. The mineral does not break along flat surfaces because there are no particular directions of weakness in its crystal structure.
54DensityA substance's density is the amount of mass in a given volume of the substance. For example, 1 cubic centimeter of the mineral pyrite has a mass of 5.1 grams, so pyrite's density is 5.1 grams per cubic centimeter.
55DensityDensity is very helpful in identifying minerals. For example, gold and pyrite look very similar. Pyrite is often called fool's gold. However, you can tell the two minerals apart by comparing their densities. Gold is much denser than pyrite. The mass of a piece of gold is almost four times the mass of a piece of pyrite of the same size.
96Characteristics of Minerals Identification of a Mineral Fill in the GraphCharacteristics of MineralsIdentification of a Mineral
97Final Jeopardy!!!!!!Use the mineral identification tests of (luster, hardness, streak and the acid test) that we conducted in class to identify the mineral at your table? Record you answers on a sheet of notebook paper. Then use your notebook paper to choose the correct mineral name from the handout at your table.
98SCRATCHES ALL COMMON MATERIALS Final Jeopardy!!!!!!Fill in the Mohs hardness scale that we used in class during our experiments?Mohs Scale12345678910COMMON TESTSSCRATCHES ALL COMMON MATERIALS