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Mineral Crystals and Major Mineral Groups Section 5.2

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MI-2 Performance Tasks 2. Describe the factors that determine how minerals grow. 3. Distinguish between minerals by the six basic mineral shapes. 1.Define and describe crystal structure.

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How did these mineral crystals grow to be so large?

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MexicoMexico's Cueva de los Cristales (Cave of Crystals) contains some of the world's largest known natural crystalstranslucent beams of gypsum as long as 36 feet (11 meters). Volcanic activity that began about 26 million years ago created Naica mountain and filled it with high-temperature anhydrite gypsum. When magma underneath the mountain cooled and the temperature dropped, the anhydrite began to dissolve and for millions of years have been deposited in the caves in the form of huge selenite gypsum crystals.

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Factors that determine crystal size: 1.Time 2.Space 3.Temperature 4.Pressure 5.Concentration Largest uncut diamond found in the Letseng Mine in southern Africa. A near-flawless white gem weighing nearly 500 carats. It was discovered on Sept. 8, 2008 It weighs 478 carats, with very few inclusions and of outstanding color and clarity.

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1. TIME and mineral formation The RATE at which the molten magma cools determines the crystal size.

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If the magma cools at a s-l-o-w rate then the crystals will. * (example: granite) be LARGE and well-formed #44

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If the magma cools at a fast rate, quickly, then the crystals will. *example: obsidian cools instantly so it has no crystal structure, but a glass-like structure be small / microscopic / not well-formed / none

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Summarize in a sentence: So. To grow the biggest, best synthetic diamond crystal, you would. time, space, cooling rate (temperature) pressure concentration

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It takes Gemesis Diamond Co. four days to grow a diamond of an average 2.5 carats. The process begins by placing a microscopic diamond grain into a 4,000-pound machine about the size of a kitchen oven. Under hundreds of thousands of pounds of pressure and at temperatures as high as 2,700 F, the nugget grows, one atom at a time. It uses about 20 kilowatt-hours per carat, The Gemesis process mimics a diamond's development deep underground. Apollo Diamond, based near Boston, takes a different tack, imitating the way diamonds are made in space. Through chemical vapor deposition, Apollo's process pumps gas into a chamber that essentially rains carbon and forms a diamond nugget from a "seed" within two to four weeks time. http://www.youtube.com/watch?v=48NoIICJ2CQ February 14, 2007 3:19 PM PST Synthetic diamonds still a rough cut By Elsa Wenzel Staff Writer, CNET NewsElsa Wenzel

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Classzone Internet Investigation ES0506 How Do Crystals Grow? 2. Space 3. Temperature 4. Pressure 5. Concentration http://www.classzone.com/books/earth_science/terc/content/investigations/es05 06/es0506page01.cfm?chapter_no=05

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Part A: Make and define a crystal The regular repeating dendrite (branching) pattern of crystals

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Part B Concentration and Crystal Formation Dead Sea: salinity level 33.7% (8.6 times saltier than any ocean)

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Part C Space and Crystal Size Classzone.com activity ES0506

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Part D The effect of the rate of crystal cooling on crystal size and formation Phenyl salicylate (salol): What happens to the crystal size formation when it cools slowly? When it cools quickly?

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________: clear, whitish, transparent _______________: pink, salmon-colored ___________________: black, gray, dull ________________: black, shiny quartz Feldspar (potassium) Hornblende (amphibole ) Mica - biotite Granite contains three main minerals. Part E Cooling Rate and the Crystal Size of Granite

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Each mineral melts / crystallizes at its own temperature between 1200C and 500C Hornblende

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Rank the order in which the minerals in granite will crystallize. First to cool and crystallize ___________ 2 nd to crystallize ___________________ 3 rd to crystallize ___________________ Last to crystallize _________________ Hornblende (amphibole) Feldspar (potassium) - pink quartz So... Quartz is the LAST to crystallize, so it is usually shapeless. Biotite mica

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Part F1 Potassium nitrate crystals Salt crystals Borax crystals

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Crystal Shapes (page 99) Crystal: the orderly arrangement of the ions, atoms and molecules determines the shape of each minerals crystals.

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Part F2: Crystal Shape Activity In your note book: Paper model letter Crystal name Example Mineral name Tray sample 1 2 3 4 5 6 Use table on page 99 in your text book F3 : Look at the crystal samples in the trays under the stereoscopes. Match them to the crystal models. A C F D B E Cubic Tetragonal Hexagonal Orthorhombic Monoclinic triclinic Halite (Salt) Zircon Emerald Topaz Sulfur Gypsum Mica turquoise

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Minerals as Gems

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Mineral Gemstones A gemstone is defined as Whats the difference between precious and semi-precious stones? What does it mean?

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Tumbled Gems Stones Gems are valued for their reflective properties due to the way they cut (facets).

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Rough, uncut vs. polished unpolished Malachite Turquoise Opal topaz emerald

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Our State Mineral Top 5 facts 1.What is the name of our state mineral? 2.What color is our state mineral? 3. What elements, the chemical formula 4. Mineral characteristics 5. How its formed 6. It is found where in Illinois. 7 Value and uses as a mineral resource What group of minerals does it belong to

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State Mineral Quiz 1.What is the name of our state mineral? 2.What two elements make up our state mineral? 3.It was formed by which method: magma process, heat/pressure, evaporation/precipitation 4. Where in the state is/was it mined? 5. What is an unusual characteristic of it?

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5-4-3-2-1 Home work! List the 5 characteristics of a mineral Describe 4 factors and how they effect crystal size Describe 3 ways that mineral form Diagram 2 polymorph forms of carbon Name the 1 most abundant mineral group in the earths crust