granite - teaching student specimens of typical granite- Unit of 5 specimens

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Teaching student specimens of a typical granite - Unit of 5 specimens
Granite is an intrusive igneous rock composed primarily of feldspar, quartz and mica. At least 35%of the feldspar is white to pink orthoclase, and quartz is at least 20% of the rock by volume. The mica in this granite is biotite. During the Cretaceous it intruded the Jurassic granodiorite of the Sierra Nevada batholith and forms a light colored mass on its eastern slope at Sand Canyon in Inyo County, California. Granite's extrusive equivalents are rhyolite, pumice and tuff.
Granites range in color from white like this one to pink, with the orthoclase feldspar giving it the characteristic shade. The granodiorite of the batholith is much darker, with dacite its extrusive equivalent. True granites are not common. Elementary and secondary students would be correct in calling anything that looks like granite "granitic," and should recognize that an accurate identification is done by experienced geologists and by specialists in petrography. Granitic rocks are a large family and "granitic" is more than acceptable. Students in a geology course who can distinguish between quartz and potassium/sodium feldspars and who can determine the percentages of each in a hand specimen, should be able to say this is 'true" granite.
The photos show granite boulders and a boulder exfoliating at Sand Canyon, Kern County, California. The third photo shows a nearby granodiorite boulder with a prominent dike running through it. Notice how much darker the granodiorite is than the granite. Granodiorite is intermediate in composition between granite and basalt, is the intrusive equivalent of dacite and is close in composition to andesite.
We really don't like the tiny finger nail-sized specimens offered to students, as we feel these are too small to see rock textures and too small for examining the identifying characteristics of a mineral. We want the "Oh, Wow!" effect when students see the set of specimens they are going to work with. We collect these specimens so that five specimens, or possibly six, will fit in a small flat rate box, and we keep the price low, as we know these will be used in a classroom. For teachers we count like a baker and a dozen is more than 12, since you will always need a few spares.  If you are a teacher, let us know.
You are buying a unit of five student specimens. The photo is representative of what we ship.
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Ships in a small Priority Mail flat rate box unless combined with other purchases. We always combine shipping to get your purchase to you at the lowest cost. We do not charge for handling. We refund any overpayments on shipping beyond our actual cost. A second unit moves the shipment into a larger box. We can generally ship 4 to 5 student units or a number of hand specimens in that box with no further increase in postage.
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