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Minerals Minerals are defined as (1) naturally occurring, (2) inorganic substances with a narrow range of (3) chemical composition and (4) characteristic.

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Presentation on theme: "Minerals Minerals are defined as (1) naturally occurring, (2) inorganic substances with a narrow range of (3) chemical composition and (4) characteristic."— Presentation transcript:

1 Minerals Minerals are defined as (1) naturally occurring, (2) inorganic substances with a narrow range of (3) chemical composition and (4) characteristic physical properties. An example: The naturally occurring form of the compound sodium chloride is the mineral halite.

2 Minerals Minerals may be subdivided into two majors groups: –SILICATES –NON-SILICATES

3 Minerals Silicates are by far the most abundant mineral group accounting for more than 90% of the Earth's crust. Silicates are the major rock-forming minerals. It follows that oxygen and silicon are the most abundant elements in the crust.

4 Minerals The basic building block of the silicates is the silica tetrahedron. Each silicon atom is attached to four oxygen atoms by tetahedral bonds. This results in a 4- charge on the Si04 group.

5 Minerals There are many ways in which the SiO4 tetrahedra can be assembled to build neutral silicate mineral structures. These structures are the major rock-forming minerals. Isolated tetrahedra balanced by the cations magnesium (Mg), iron (Fe),calcium (Ca) –Olivines (Mg, Fe) 2 SiO 4, Magnesium Iron SilicateOlivines –and GarnetsGarnets

6 Minerals The typical pyroxene structure contains chains of SiO 3 tetrahedrons The slope of the tetrahedral pyramids helps to determine the cleavage angle of the pyroxenes at nearly 90 o degrees (actually 93 o and 87 o ).

7 Minerals common amphiboles: Actinolite Ca 2 (Mg, Fe +2 ) 5 Si 8 O 22 (OH) 2 Anthophyllite (Mg, Fe) 7 Si 8 O 22 (OH) 2 Arfvedsonite Na 3 (Fe +2 ) 4 Fe +3 Si 8 O 22 (OH) 2 Cummingtonite Mg 7 Si 8 O 22 (OH) 2 Edenite NaCa 2 Mg 5 Si 8 O 22 (OH) 2 Fluorrichterite Na(CaNa)Mg 5 Si 8 O 22 F 2 Glaucophane Na 2 (Mg 3 Al 2 ) Si 8 O 22 (OH) 2 The Hornblende Series Ca 2 (Mg, Fe +2 ) 4 (Al, Fe +3 )Si 7 AlO 22 (OH) 2 Double chains of tetrahedra balanced by similar cations.

8 Minerals Micas and Clay MineralsMicas Sheets of tetrahedra are the building blocks. Aluminum is also involved in these sheet structures which are charge-balanced by the cations Mg, Na and K. most common mica minerals: muscovite, biotitemuscovite biotite

9 Minerals Feldspars A second group of alumino-silicates, tetrahedra form three- dimensional frameworks with Ca, Na and K as the balancing cations. The very abundant feldspar are subdivided in K-Na bearing alkali feldspars and the Ca-Na solid-solution series called the plagioclase feldspars.

10 Minerals Feldspars A second group of alumino-silicates, tetrahedra form three- dimensional frameworks with Ca, Na and K as the balancing cations. The very abundant feldspar are subdivided in K-Na bearing alkali feldspars and the Ca-Na solid-solution series called the plagioclase feldspars. The K-feldspars or alkali felspars: Microcline, (Potassium aluminum silicate)Microcline Sanidine, (Potassium sodium aluminum silicate)Sanidine Orthoclase, (Potassium aluminum silicate)Orthoclase

11 Minerals Feldspars A second group of alumino-silicates, tetrahedra form three- dimensional frameworks with Ca, Na and K as the balancing cations. The very abundant feldspar are subdivided in K-Na bearing alkali feldspars and the Ca-Na solid-solution series called the plagioclase feldspars. The plagioclase feldspars: Albite, (Sodium aluminum silicate)Albite Oligoclase, (Sodium calcium aluminum silicate)Oligoclase Andesine, (Sodium calcium aluminum silicate)Andesine Labradorite, (Calcium sodium aluminum silicate)Labradorite Bytownite, (Calcium sodium aluminum silicate)Bytownite Anorthite, (Calcium aluminum silicate)Anorthite

12 Minerals Quartz Silica tetrahedra alone can form a neutral three-dimensional framework structure with no need for other cations. This arrangement forms a very stable structure popular as ornamental stone and as gemstones Amethyst is the purple gemstone variety.Amethyst Citrine is a yellow to orange gemstone variety that is rare in nature but is often created by heating Amethyst.Citrine Milky Quartz is the cloudy white variety.Milky Quartz Rock crystal is the clear variety that is also used as a gemstone.Rock crystal Rose quartz is a pink to reddish pink variety.Rose quartz Smoky quartz is the brown to gray variety.Smoky quartz

13 Minerals Quartz SiO4Quartz Silica tetrahedra alone can form a neutral three-dimensional framework structure with no need for other cations. This arrangement forms a very stable structure popular as ornamental stone and as gemstones Amethyst is the purple gemstone variety.Amethyst Citrine is a yellow to orange gemstone variety that is rare in nature but is often created by heating Amethyst.Citrine Milky Quartz is the cloudy white variety.Milky Quartz Rock crystal is the clear variety that is also used as a gemstone.Rock crystal Rose quartz is a pink to reddish pink variety.Rose quartz Smoky quartz is the brown to gray variety.Smoky quartz

14 Minerals Quartz Silica tetrahedra alone can form a neutral three-dimensional framework structure with no need for other cations. This arrangement forms a very stable structure popular as ornamental stone and as gemstones Amethyst is the purple gemstone variety.Amethyst Citrine is a yellow to orange gemstone variety that is rare in nature but is often created by heating Amethyst.Citrine Milky Quartz is the cloudy white variety.Milky Quartz Rock crystal is the clear variety that is also used as a gemstone.Rock crystal Rose quartz is a pink to reddish pink variety.Rose quartz Smoky quartz is the brown to gray variety.Smoky quartz

15 Minerals Quartz Silica tetrahedra alone can form a neutral three-dimensional framework structure with no need for other cations. This arrangement forms a very stable structure popular as ornamental stone and as gemstones Amethyst is the purple gemstone variety.Amethyst Citrine is a yellow to orange gemstone variety that is rare in nature but is often created by heating Amethyst.Citrine Milky Quartz is the cloudy white variety.Milky Quartz Rock crystal is the clear variety that is also used as a gemstone.Rock crystal Rose quartz is a pink to reddish pink variety.Rose quartz Smoky quartz is the brown to gray variety.Smoky quartz

16 Minerals There are a few important groups of non-silicate minerals. Only the carbonates are significant as rock-forming minerals. The remaining mineral groups are often ore minerals and provide economic sources for various elements. The important non-silicate groups are: –CarbonatesCarbonates –Evaporites –OxidesOxides –SulphidesSulphides –PhosphatesPhosphates

17 Non silicates: Carbonates: CO 3Carbonates The important carbonates are the minerals calcite and dolomite. Both are significant rock-forming minerals. The Calcite Group:Calcite Group: Calcite (Calcium Carbonate)Calcite Gaspeite (Nickel Magnesium Iron Carbonate)Gaspeite Magnesite (Magnesium Carbonate)Magnesite Otavite (Cadmium Carbonate)Otavite Rhodochrosite (Manganese Carbonate)Rhodochrosite Siderite (Iron Carbonate)Siderite Smithsonite (Zinc Carbonate)Smithsonite Sphaerocobaltite (Cobalt Carbonate)Sphaerocobaltite Minerals

18 Non silicates: Evaporites: halides including the minerals halite, sylvite and fluorite; sulphates including the minerals gypsum and anhydrite. halides sulphates The most famous halide mineral, halite (NaCl) or rock salt

19 Minerals Non silicates: Evaporites: halides including the minerals halite, sylvite and fluorite; sulphates including the minerals gypsum and anhydrite. halides sulphates Fluorite: CaF2, Calcium Fluoride

20 Minerals Non silicates: Evaporites: halides including the minerals halite, sylvite and fluorite; sulphates including the minerals gypsum and anhydrite. halides sulphates Gypsum:CaSO4-2(H2O), Hydrated Calcium Sulfate

21 Minerals Non silicates: Oxides oxides (hematite and magnetite) hydroxides (limonite and goerthite) important minor consituents in rocks. aluminum oxide bauxite can also occur as a rock-forming mineral. oxide minerals are exploited as economic sources of many elements including aluminum, antimony, iron, manganese, tin, and uranium.

22 Minerals Non silicates: Oxides oxides (hematite and magnetite) Fe2O3, Iron Oxide hydroxides (limonite and goerthite) important minor consituents in rocks. aluminum oxide bauxite can also occur as a rock-forming mineral. oxide minerals are exploited as economic sources of many elements including aluminum, antimony, iron, manganese, tin, and uranium.

23 Minerals Non silicates: Oxides oxides (hematite and magnetite) Fe3O4, Iron Oxide hydroxides (limonite and goerthite) important minor consituents in rocks. aluminum oxide bauxite can also occur as a rock-forming mineral. oxide minerals are exploited as economic sources of many elements including aluminum, antimony, iron, manganese, tin, and uranium.

24 Minerals Non silicates: Sulphides The mineral pyrite is the only sulphide that occurs commonly in rocks. Sulphides are most important as economic minerals providing the main sources of elements such as arsenic, copper, lead, nickel, mercury, molybdenum and zinc. FeS2, Iron Sulfide

25 Minerals Non silicates: Sulphides The mineral pyrite is the only sulphide that occurs commonly in rocks. Sulphides are most important as economic minerals providing the main sources of elements such as arsenic, copper, lead, nickel, mercury, molybdenum and zinc. PbS, Lead Sulfide, Galena

26 Minerals Non silicates: Sulphides The mineral pyrite is the only sulphide that occurs commonly in rocks. Sulphides are most important as economic minerals providing the main sources of elements such as arsenic, copper, lead, nickel, mercury, molybdenum and zinc. CuFeS2, Copper Iron Sulfide, Chalcopyrite

27 Minerals Non silicates: Phosphates are relatively rare. The only important phosphate mineral is apatite. Ca2Fe(PO4)2 - 4H2O, Hydrated Calcium Iron Phosphate

28 Mineral properties Minerals are distinguished by their physical and chemical properties. The same properties are responsible for the many of the mechanical characteristics of rocks. Most common minerals can be recognized from one or two characteristics.

29 Mineral properties PHYSICAL CHARACTERISTICS: 1. Colour The colour of minerals is rarely diagnostic when used alone but some minerals (native sulphur - YELLOW, amethyst quartz - PURPLE, hematite - RED, azurite - BLUE GREEN) are very distinctively coloured.

30 Mineral properties PHYSICAL CHARACTERISTICS: 2. Lustre Lustre is the way in which light is reflected from mineral surfaces and is more frequently diagnostic than colour. Metallic lustre is often found in sulphide minerals, non-metallic lustres include glassy, dull and earthy.

31 Mineral properties PHYSICAL CHARACTERISTICS: 3. Transparency The ability to see through a mineral is a measure of transparency. Reflecting surfaces are called translucent.

32 Mineral properties PHYSICAL CHARACTERISTICS: 4. Crystal System Crystal symmetry is a very important diagnostic aid. Minerals fall into one of seven crystal classes.

33 Crystal System ISOMETRIC DIAMOND TETRAGONAL WULFENITE HEXAGONAL BERYL TRIGONAL QUARTZ variety - AMETHYST ORTHORHOMBIC TANZANITE MONOCLINIC GYPSUM TRICLINIC MONTEBRASITE AMORPHOUS AMBER

34 Crystal System SEVEN CRYSTALLOGRAPHIC SYSTEMS: 1.ISOMETRIC, requires 4 three fold axis of rotation. ISOMETRIC 2.TETRAGONAL, requires 1 four fold axis of rotation. TETRAGONAL 3.HEXAGONAL, requires 1 six fold axis of rotation. HEXAGONAL 4.TRIGONAL, requires 1 three fold axis of rotation. TRIGONAL 5.ORTHORHOMBIC, requires either 3 two fold axis of rotation or 1 two fold axis of rotation and two mirror planes. ORTHORHOMBIC 6.MONOCLINIC, requires either 1 two fold axis of rotation or 1 mirror plane. MONOCLINIC 7.TRICLINIC, requires either a center or only translational symmetry. AMORPHOUS; no symmetry is present and it is therefore not a crystallographic system.TRICLINIC

35 Mineral properties PHYSICAL CHARACTERISTICS: 5. Crystal Habits This is the name given to the form or shape of crystals. Cubic, dodecahdral, octahedral, rhombohdral, prismatic, columnar, pinacoidal and pyramidal are a few of the many forms that crystal can display.

36 Mineral properties PHYSICAL CHARACTERISTICS: 6. Cleavage This refers to the characteristic manner in which minerals split along planes determined by their crystal structure. Mica has a perfect basal cleavage in one direction and splits into thin sheets. Feldspars commonly show two strong cleavages. Cubic minerals such as halite often display three mutually orthogonal cleavage directions.

37 Mineral properties PHYSICAL CHARACTERISTICS: 7. Fracture Fracture is mineral breakage which is unrelated to crystal structure. Quartz has no cleavage but can often show conchoidal fracture patterns.

38 Mineral properties PHYSICAL CHARACTERISTICS: 8. Hardness Mineral hardness is measured on a non-linear relative scale called Mohs Scale of HardnessMohs Scale of Hardness

39 Mineral properties PHYSICAL CHARACTERISTICS: 8. Hardness Mineral hardness is measured on a non-linear relative scale called Mohs Scale of Hardness Mohs Scale of Hardness HARDNESS MINERALCOMMON EXAMPLE 1TalcPencil lead GypsumFingernail 2.5 3CalciteCopper penny 3.5, brass 4FluoriteIron 5ApatiteTooth enamel, knife blade, glass OrthoclaseSteel file 6.5 7QuartzScratches glass 8Topaz CorundumSaphire, ruby 10DiamondSynthetic diamond

40 Mineral properties PHYSICAL CHARACTERISTICS: 9. Specific Gravity S.G. is an easily measured physical property that can be readily estimated. In general, sulphides and oxides have much higher specific gravities than silicates.

41 Mineral properties PHYSICAL CHARACTERISTICS: 9. Specific Gravity S.G. is an easily measured physical property that can be readily estimated. In general, sulphides and oxides have much higher specific gravities than silicates. MINERAL GROUPMINERALSPECIFIC GRAVITY Framework SilicateQuartz Framework SilicateFeldspar Sheet SilicateMica Chain SilicateAmphibole Chain SilicatePyroxene Isolated SilicateOlivine Isolated SilicateGarnet SulphideSphalerite4.0 SulphideChalcopyrite4.2 SulphidePyrite5.0 OxideMagnetite5.2 OxideHematite5.3 SulphideGalena7.2 OxidePitchblende9.5 ElementNative Gold12.4

42 Mineral properties PHYSICAL CHARACTERISTICS: 10. Streak Streak is the name given to the colour of a mineral when powdered by abraision against a stronger material (usually a ceramic or porcellain plate). Streak is a much more useful diagnostic characteristic than colour.

43 Mineral properties PHYSICAL CHARACTERISTICS: 11. Other Characteristics: Some minerals have special characteristics that are diagnostic for only a few species. Refractive index (calcite), effervescence with dilute acids (calcite), fluorescence (fluorite), phosphorescence, piezoelectricity (quartz), resistivity (halite), taste (halite) and magnetic properties (magnetite) are all used to identify particular minerals.

44 Common minerals the most common minerals you'll find in rocks ”rock forming minerals” This pile contains plagioclase feldspar, potassium feldspar, quartz, muscovite mica, biotite mica, amphibole, olivine, and calcite.plagioclase feldsparpotassium feldsparquartzmuscovite micabiotite mica amphiboleolivinecalcite

45 Lab - common minerals You must print out the instructions from internet Your are to work in groups First read the entire mineral lab instructions Your are to try to identify the minerals by determining their physical properties (check in the course text book chapter 2) When you think you have identified them correctly – ASK an assistent to check them Learn to recognize them Change boxes with another group and test if you can identify them when they look a bit differently Check the minerals that are in the large demonstration boxes at the front of the class to see how differently they look

46 Minerals – what you need to know! Oral test –Name of the mineral and –Mineral group –Limited time, 5 min Written test –Definition of a mineral –Physical properties of minerals –Hardness scale –Mineral groups –Recognize the mineral names we learn in the lab as a mineral


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