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GEMSTONES By Audree,Jordan,Josh , and Alex. A gemstone or gem (also called a precious or semi-precious stone) is a piece of attractive mineral, which when cut and polished is used to make jewelry or other decorations.

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GEMSTONES

By Audree,Jordan,Josh, and Alex

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A gemstone or gem (also called a precious or semi-precious stone) is a piece of attractive mineral, which when cut and polished is used to make jewelry or other decorations.

Precious: Has beauty, durability, size, and rarity.(Diamond, emerald, opal,ruby,safphire)

Semi-precious: only two of those (quartz, Jade)

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The Mohs Scale characterizes the scratch resistance of different types of minerals through the ability of a harder material to scratch a softer material. It was created in 1812 by the German mineralogist Friedrich Mohs.

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Most gemstones are hard, but some soft minerals are used in jewelry because of their luster or other physical properties that have value.

Luster: the way light interacts with the surface of a crystal, rock, or mineral.Sheen.

Greasy Luster

Greasy minerals resemble fat or grease. A greasy lustre often occurs in minerals containing a lot of microscopic inclusions. Some examples are opal and cordierite.Many minerals with a greasy lustre also feel greasy or smooth.

Adamantine Luster

Adamantine minerals have the best lustre. It is mostly seen in diamond.Diamond minerals are transparent and refract the light the best.Minerals with a true adamantine lustre are uncommon.

Dull Luster

Dull (or earthy) minerals have little to no lustre, because they are coarse and grainy, which scatters light in all directions instead of reflecting it. These minerals are not used for jewlery or decorations.

Metallic Luster

Metallic minerals have the lustre of polished metal.

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Pearly Luster

Pearly minerals consist of thin transparent sheets. Light reflecting from these layers give them a lustre similar to Pearls.

Submetalic Luster

Submetallic minerals have similar lustre to metal, but are duller and less reflective

Resinous Luster

Resinous minerals have the appearance of chewing gum chewing or plastic

Waxy luster

Vitreous Luster

Vitreous minerals have the lustre of glass. This type of lustre is one of the most commonly seen, and occurs in transparent or translucent minerals

Silky Luster

Silky minerals have a parallel arrangement of fine fibers. This makes the minerals look like silk.

minerals have a luster resembling wax.

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Magmatic Crystallization: Cooling Magma produces crystals of different kinds of minerals. Crystals are formed from the lava when the volcano erupts. Examples: moonstone, topaz and corundum.

Metamorphic deposits: When a rock is in a high temperature and or high pressure, the chemical components get rearranged into new minerals. Gem minerals formed are diopside, corundum, andalusite, sillimanite, kyanite, epidote, and garnet.

Pegmatite: Towards the final stage of magmatic crystallisation, a thin silicate liquid remains and if this is squeezed into surrounding rocks, it produces pegmatites containing very large crystals. Examples:Tourmaline, topaz, beryl, quartz and spodumene are some of the common pegmatitic gem stones.

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Metamorphic deposits: When a rock is in a high temperature and or high pressure, the chemical components get rearranged into new minerals. Gem minerals formed are diopside, corundum, andalusite, sillimanite, kyanite, epidote, and garnet.

Placer or Alluvial deposits: Some minerals are highly resistant to weathering and when the rest of the rock has decomposed and disintegrated they are carried by flowing water.Because of gravity, they get deposited on the river bed making a gem.Examples:diamond, ruby, sapphire, chrysoberyl, zircon, garnet,and quartz

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topaz, beryl, quartz

moonstone, topaz and corundum

diamond, ruby, sapphire

kyanite, epidote, and garnet

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RESOURCES

http://images.google.com/imgres?imgurl=http://www.eoearth.org/media/approved/3/3c/Mohs.jpg&imgrefurl=http://www.eoearth.org/article/Mohs,_Frederick&usg=__wRdbD8V99xE1XCIAy_h-EyRWREE=&h=200&w=149&sz=16&hl=en&start=13&um=1&tbnid=DfUA1xqC7KT6BM:&tbnh=104&tbnw=77&prev=/images%3Fq%3Dfrederick%2Bmohs%26hl%3Den%26safe%3Dactive%26rlz%3D1T4GGLL_enUS355US355%26sa%3DN%26um%3D1

http://en.wikipedia.org/wiki/Gemstone

http://en.wikipedia.org/wiki/Lustre_(mineralogy)

http://www.okaloosa.k12.fl.us/technology/WOWLessons/WOWResources/RockCycleDiagram.gif

http://www.gemstonebuzz.com/gemstone-formation

http://images.google.com/imgres?imgurl=http://www.gbgold.co.uk/imgs/Coloured%2520Gemstones.jpg&imgrefurl=http://www.gbgold.co.uk/%3Fpage%3Dcertified%26id%3D5&usg=__ZPEiNJWIkyaqCk3Qt_LS1XA9S_g=&h=334&w=500&sz=256&hl=en&start=17&um=1&tbnid=Dl34Ise-CR853M:&tbnh=87&tbnw=130&prev=/images%3Fq%3Dgemstones%26hl%3Den%26safe%3Dactive%26rlz%3D1T4GGLL_enUS355US355%26sa%3DN%26um%3D1

http://images.google.com/imgres?imgurl=http://www.anywherecostarica.com/special/arenal-volcano-sunrise/arenal-volcano-night-lava.jpg&imgrefurl=http://www.anywherecostarica.com/special/arenal-volcano-sunrise/&usg=__KYFVAgCHmPJkOGd1eiZZPOy8zIU=&h=479&w=700&sz=44&hl=en&start=11&um=1&tbnid=hcvBp4kwz9IDjM:&tbnh=96&tbnw=140&prev=/images%3Fq%3Dvolcano%26hl%3Den%26safe%3Dactive%26rlz%3D1T4GGLL_enUS355US355%26sa%3DN%26um%3D1

http://www.google.com/imgres?imgurl=http://stloe.most.go.th/html/lo_index/LOcanada2/203/images/2_3_4en.jpg&imgrefurl=http://stloe.most.go.th/html/lo_index/LOcanada2/203/4_en.htm&h=400&w=400&sz=55&tbnid=osMqrvONSLoyWM:&tbnh=124&tbnw=124&prev=/images%3Fq%3Dmohs%2Bscale&usg=__vQHxsIgoYsq63fr0YoUsZmGsx38=&ei=HU1OS5GeK4qCswPB4MSDCA&sa=X&oi=image_result&resnum=6&ct=image&ved=0CBQQ9QEwBQ

http://en.wikipedia.org/wiki/Mohs_scale_of_mineral_hardness