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Mineral Lab

Mineral Lab. Goals of mineral section. What is a mineral? How are physical and chemical properties used to identify minerals? Which elements are found in the major rock forming minerals? Where on the periodic table are the most abundant elements located?. Definition of a mineral.

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Mineral Lab

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  1. Mineral Lab

  2. Goals of mineral section • What is a mineral? • How are physical and chemical properties used to identify minerals? • Which elements are found in the major rock forming minerals? • Where on the periodic table are the most abundant elements located?

  3. Definition of a mineral • Inorganic minerals can be defined as naturally occurring, solids, with a unique combination of elements that are arranged in a specific way

  4. What is not a mineral • Substances must meet all of these criteria to be classified as minerals – coal, for example, is not a mineral since it is formed from once living material. Opals have no distinct arrangement, so they are not classified as minerals. Man-made gemstones are not minerals, either.

  5. How many minerals Minerals are the building blocks of rocks. There are more than 4000 minerals with about 100 of them being fairly common. Of the 100 common minerals about 20 are the major rock forming minerals.

  6. Mineral classification • Minerals are identified based on their physical and chemical properties. When thinking about volcanoes and igneous rocks, minerals are the crystals that form when magma cools. Many of the igneous rocks are classified (or named) based on the size of these crystals and the assemblage of minerals found in the rock.

  7. Goals of lab • Examine the different physical and chemical properties of minerals. • Identify 9 of the major rock forming minerals based upon observed properties. • Identify the elements that occur most often in some of the major rock forming minerals • Determine the position on the periodic chart of the most common elements. • Given their position on the periodic chart, make a prediction about the density of the minerals that contain these elements.

  8. Main ideas covered in lab • The various physical and chemical properties (e.g., hardness, streak, density, luster, cleavage, color, and reaction with hydrochloric acid) of minerals can be used to identify them. • The major rock forming minerals are composed of a relatively few number of elements. • The positions of these elements on the periodic table provide clues to some of the properties of the minerals that contain these elements.

  9. Physical properties • Color – Color is a physical property that is readily observable. Unfortunately, color is not always a useful property because some minerals occur in many different colors. For example, shown below is the mineral quartz occurring with three different colors. The colors in quartz are generally determined by the presence of small, or trace, amounts of other elements like aluminum, iron, and titanium which affect light as it passes through the mineral or is reflected.

  10. Quartz samples from U of D

  11. Physical property: Luster • Luster – Luster is the appearance of a mineral in reflected light. For example, if it looks like metal then it has a metallic luster; if it doesn’t look like metal then it has a non-metallic luster. Non-metallic minerals may be described as having glassy, dull, silky, greasy, or brilliant luster.

  12. Examples of luster • Gold (metallic luster) • Amethyst Quartz (non-metallic glassy luster)

  13. Hardness • Hardness – Hardness is the ability of a mineral to resist being scratched. The degree of hardness is described on a scale called the Moh’s hardness scale. Moh’s hardness scale goes from 1 to 10. With 1 being the softest (the mineral talc) and 10 being the hardest (the mineral diamond). To estimate the degree of hardness, some common comparisons can be used. For example, a mineral is considered soft (having a hardness less than 2-3) if it can be scratched by a fingernail or a penny. A mineral is considered hard if it can scratch glass (hardness of 5.5) and it cannot be scratched by a steel file (Hardness of 6.5). The mineral quartz has a high degree of hardness equal to 7 on Moh’s Hardness scale.

  14. Lines of breakage (cleavage) Cleavage is a physical property that describes the way a mineral breaks. Minerals may cleave (or break) in 1, 2, 3, 4, 6 directions, at different angles or may not cleave at all. Generally the cleaving, or breaking, occurs along planes of weakness in the mineral. The elements along these planes have relatively weaker bonds.

  15. Biotite (1 line of breakage) • Quartz (0 lines of cleavage)

  16. Streak • Streak – Streak is the color of the powder left by a mineral. Some minerals leave streaks that are the same color as the mineral, others leave streaks that are a different color than the mineral.

  17. Density • Density– The density, or specific gravity, is the ratio of the mass of the mineral relative to its volume. The density of minerals can vary greatly, for example, gold is 3 times more dense than pyrite (“fools” gold).

  18. Reactivity • Reaction to HCl

  19. Mineral observation chart

  20. Mineral Clue Sheet Albite (Plagioclase Feldspar) – white to gray in color, glassy luster, 2 planes of cleavage that meet at 90o, white streak, can scratch glass Biotite Mica – black to brownish black, very flat surface (1 plane of cleavage), can peel into thin sheets, no streak, glassy luster. Calcite - usually white or clear, white streak, will fizz with HCl acid, can scratch with a penny, rhombohedral shape showing 3 planes of cleavage, glassy luster. Hornblende – shiny black to brownish black in color, 2 planes of cleavage that meet at 60o or 120o, glassy luster, no streak, may/may not scratch glass Microcline (Orthoclase Feldspar) – colorless to white, yellowish, reddish, or green, glassy luster, 2 planes of cleavage that meet at 90o, white streak, can scratch glass Milky Quartz- white or milky color, glassy luster, no streak, can scratch glass, no cleavage. Muscovite Mica- colorless but may be tinted gray, very flat surface (one plane of cleavage), can peel into in thin sheets, no streak, glassy luster. Olivine – light to dark green in color, glassy luster, no streak, can scratch glass, no cleavage Pyroxene – dark green to black in color, glassy luster, no streak, may/may not scratch glass, 2 planes of cleavage that meet at 90o

  21. Chemical formulas of minerals • Minerals are composed of unique combinations of elements and these elements are arranged in a specific way. • The composition of minerals is expressed by their chemical formulas.

  22. Chemical Formulas of Minerals Albite (Plagioclase Feldspar) – Na(AlSi3O8) Biotite Mica – K(Mg,Fe)3(AlSi3O10)(OH,F)2 Calcite – Ca(CO3) Hornblende – Ca2(Fe,Mg)4Al(AlSi7O22)(OH)2 Microcline (Orthoclase Feldspar) – K(AlSi3O8) Muscovite Mica – KAl2(AlSi3O10)(OH,F)2 Olivine – (Mg,Fe)2(SiO4) Pyroxene – (Fe,Mg)2(Si2O6) Quartz – SiO2

  23. Questions based on lab 1. What are the five most common elements that occur in these minerals? 2. What are three common building blocks or structures (portions of a formula found in parentheses) that you observe within these minerals? 3. What are some elements that can substitute for each other in these minerals?

  24. Questions based on lab • 4. In your journal, record observations about these elements based on their positions on the periodic table. • Do they occur in any common groups on the periodic table? • If so, what are the groups? • Which elements are metals; which are non-metals?

  25. Questions based on lab • 5. Based on their chemical formulas, the elements that compose the minerals, and the position of these elements on the periodic table, for each of these pairs of minerals, which do you think would have the greatest mass, and with equal volumes, the highest density? Justify your answer. • Olivine vs. Quartz? • Pyroxene vs. Microcline (Orthoclase Feldspar)? • Biotite Mica vs. Muscovite Mica?

  26. Granite –VS- Basalt Granite is an igneous rock that is composed of the minerals quartz, orthoclase feldspar, muscovite mica, with lesser amounts of biotite mica, plagioclase feldspar, and biotite mica. Granite is the igneous rock that is associated with the continents. Basalt is an igneous rock that is composed primarily of the minerals olivine, pyroxene, plagioclase feldspar. Basalt is the igneous rock that is associated with the rocks beneath the oceans.

  27. Questions based on lab 6. Based on the minerals that comprise these rocks, which of these two rocks, granite or basalt, do you think would have the greatest weight, and with equal volumes, the higher density? Justify your answer. We will be testing your answer (or hypothesis) to this question later in this unit.

  28. Check in • How are minerals different from rocks? • How are physical and chemical properties used to identify minerals? • What are the most common elements found in the rock forming minerals and what is their general location on the periodic table?

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