Presentation on theme: "Emeralds are a form of the mineral beryl"— Presentation transcript:
1Emeralds are a form of the mineral beryl Emeralds are a form of the mineral beryl. These gems form deep beneath Earth’s surface and are found in relatively few locations.
2Minerals and RocksWhat is a mineral?A mineral is a naturally occurring, inorganic solid with a crystal structure and a characteristic chemical composition.
3A rock is a solid combination of minerals or mineral materials. Minerals and RocksA rock is a solid combination of minerals or mineral materials.Minerals are inorganic, meaning that living things did not produce them and they occur naturally.Geologists don’t classify coal as a mineral because coal was created from plant remains.Materials like brick and concrete are not considered minerals either.
4Granite is made up of quartz, feldspar, mica, and hornblende. Minerals and RocksGranite is made up of quartz, feldspar, mica, and hornblende.A magnified view reveals the individual crystals of the minerals that make up granite.FeldsparMicaQuartzHornblende
5The Properties of Minerals What are some important properties of minerals?The properties by which minerals can be identified include their crystal structure, color, streak, luster, density, hardness, fracture, and cleavage.
6The Properties of Minerals Crystal StructureIn each type of mineral, the atoms are arranged in a particular geometric shape, or crystal structure.Each mineral always has the same crystal structure.The size of a mineral’s crystals can vary.
7The Properties of Minerals Quartz that is pure silicon dioxide is clear or white. Slight impurities produce a range of colors, including the violet quartz (amethyst) specimen shown here.
8The Properties of Minerals ColorSome minerals can be identified by a characteristic color.Pyrite, also known as fool’s gold, is always golden in color.Crystals of pure sulfur are always yellow.But a mineral’s color can often be deceptive, because slight changes in composition can cause significant changes in a mineral’s color.
9The Properties of Minerals StreakThe color of a mineral’s powder is known as its streak.A mineral’s streak can be found by scraping the mineral on a piece of unglazed porcelain called a streak plate.The color of a mineral’s streak is not always the same as the color of the mineral itself.
10The Properties of Minerals Although this piece of hematite is silver-gray, it can be identified by its red-brown streak.
11The Properties of Minerals LusterLuster is the way in which a mineral’s surface reflects light.A rough, crumbly surface is said to be an earthy luster. Other terms that describe luster include silky, pearly, and vitreous (glassy.)Galena and pyrite have a metallic luster.Sulfur has a resinous-to-greasy luster.
12The Properties of Minerals DensityThe density of a mineral depends on its chemical composition.In general, minerals made up of elements with higher atomic masses have higher densities than minerals made up of atoms with lower atomic masses.
13The Properties of Minerals Galena contains much lead, which has a relatively high atomic mass of 207. Galena’s density is about 7.5 grams per cubic centimeter.Quartz is made up of silicon and oxygen, which have relatively low atomic masses of 28 and 16 respectively. Quartz’s density is only about 2.6 grams per cubic centimeter.
15Density of MineralsThe density of minerals varies, depending on what elements the minerals contain. Samples of the minerals in the data table were analyzed for density, silicon and oxygen content, and the presence of metals. Study the data table and then answer the questions.
16Density of MineralsUsing Tables Which mineral has the lowest density? The highest density?
17Density of MineralsUsing Tables Which mineral has the lowest density? The highest density? Answer: quartz; olivine
18Density of MineralsUsing Tables Which minerals have the lowest percentage of silicon and oxygen? Which has the highest?
19Density of MineralsUsing Tables Which minerals have the lowest percentage of silicon and oxygen? Which has the highest? Answer: olivine and augite; quartz
20Density of MineralsFormulating Hypotheses Olivine and augite are abundant in oceanic crust and in the mantle. Quartz, muscovite, and hornblende are abundant in continental crust. Formulate a hypothesis to explain why continental crust floats higher on the mantle than oceanic crust.
21Density of MineralsFormulating Hypotheses Olivine and augite are abundant in oceanic crust and in the mantle. Quartz, muscovite, and hornblende are abundant in continental crust. Formulate a hypothesis to explain why continental crust floats higher on the mantle than oceanic crust. Answer: Continental crust is composed of less dense minerals than oceanic crust. Therefore, continental crust is more buoyant and floats higher on the mantle.
22Density of MineralsDrawing Conclusions How is a mineral’s density related to its silicon and oxygen content?
23Density of MineralsDrawing Conclusions How is a mineral’s density related to its silicon and oxygen content? Answer: In general, the higher the silicon and oxygen content of a mineral, the lower its density.
24The Properties of Minerals HardnessThe atoms of minerals are held together by chemical bonds of different kinds and strengths.Hardness is the resistance of a mineral to scratching.
25The Properties of Minerals HardnessA hard mineral can scratch a softer mineral.The hardness of minerals is ranked on a scale from 1 to 10, called Mohs hardness scale.Diamond is the hardest mineral, with a hardness of 10.Talc is one of the softest minerals, with a hardness of 1.
26The Properties of Minerals Geologists use scratch tests to determine the hardness of mineral specimens.A glass plate has a hardness of 5.5. A mineral that scratches the plate has a hardness greater than 5.5.A copper penny, which has a hardness of about 3.5, can scratch talc, but it cannot scratch quartz.A fingernail, with a hardness of 2.5, and a streak plate, with a hardness of 6.5, can also be used to test hardness.
27The Properties of Minerals Fracture and CleavageThe fracture of a mineral is how the mineral breaks.Fracture is determined by the crystalline structure of the mineral and the bonds between the atoms in the crystals.
28The Properties of Minerals Cleavage is a type of fracture in which the mineral tends to split along regular, well-defined planes where the bonds are weakest.Mica and graphite form sheets. Each sheet contains chemical bonds that are very strong.The sheets are held together with weak bonds, so they can easily be peeled apart from each other.
29The Properties of Minerals Mica forms in thin, flat sheets that can be easily peeled apart. When halite is broken apart, it forms small cubes that show its crystal structure.
30The Properties of Minerals Other PropertiesSome minerals have unusual properties.Acids dissolve calcite easily.Magnetite is strongly attracted by a magnet.Fluorescent minerals like fluorite give off visible light when they are held under an ultraviolet light.
31The Properties of Minerals Some minerals have unusual electrical properties.Quartz and tourmaline, for example, become electrically charged when heated and cooled or subjected to pressure.Quartz’s electrical properties have applications in electronics equipment.
32Assessment QuestionsWhich of the following properties would not be used to identify an unknown mineral?crystal shapedensityhardnesssize
33Assessment QuestionsWhich of the following properties would not be used to identify an unknown mineral?crystal shapedensityhardnesssize ANS: D