Save my name, email, and website in this browser for the next time I comment. I would like a quote on What is Granite? What is Granite? Granite , June 15, by Anya. It is removed by jet piercing or drilling.
In the former, a very hot, high speed flame is used to cut a channel into the granite, and the stone is split along its grain like a piece of wood. In drilling, holes are bored into the stone. The granite between them is removed and then drilled again. After the blocks are removed, they are cut into slabs by circular saws with diamond tipped blades, then polished by machine.
Some quarries add resin to the granite to fill in tiny cracks that might compromise the stone. The slab is then polished again to take away any excess resin.
Then, the slab is inspected, carefully packaged and sent on its way to a retailer. Can you hang wallpaper in the kitchen? They will often be in "books" of numerous sheets stacked upon one another.
The surfaces of these sheets will have a highly reflective vitreous luster. The edges of a "stack of sheets" will look similar to the edge of a stack of playing cards. Amphibole minerals such as hornblende are dark in color and will often have a prismatic habit.
The best way to learn about rocks is to have specimens available for testing and examination. Granite is a plutonic rock in which quartz makes up between 10 and 50 percent of the felsic components.
Alkali feldspar accounts for 65 to 90 percent of the total feldspar content. Applying this definition requires the mineral identification and quantification abilities of a competent geologist. This type of analysis cannot be done precisely by a student in a classroom or a geologist in the field. This is an example of the complexities that can be involved in assigning a formal name to an igneous rock.
Many rocks identified as "granite" using the introductory course definition will not be called "granite" by the petrologist. They might instead be alkali granites, granodiorites, pegmatites , or aplites. These names are for specific types of granite. These names require a consideration of the grain size and the mineral composition of the rock - beyond determining that the rock is a granite.
A petrologist might call these "granitoid rocks" rather than granites. There are many types of granite based upon mineral composition and texture. The accompanying chart Generalized Composition Ranges of Common Igneous Rocks illustrates the range of granite compositions. From the chart you can see that orthoclase feldspar , quartz , plagioclase feldspar , micas, and amphiboles can each have a range of abundances. Using the terminology of geologists, they would be clockwise from top left : granite , gneiss , pegmatite , and labradorite.
Click on any of their names above for an enlarged view. Each of the images above represents a slab of polished rock about eight inches across. Use of the word "granite" in the dimension stone and crushed stone industries is different from how the word is used by geologists. In these industries, the name "granite" refers to an igneous rock that meets the following criteria:. Using these criteria, gabbro , basalt , pegmatite , schist , gneiss , diabase , diorite , and many other igneous rocks will be called "granite.
These "granites" are used to make crushed stone that is used for highway construction, concrete, building construction, fill, railroad ballast, and many other purposes. They are used in the dimension stone industry to make countertops, floor tiles, curbing, building veneer, monuments, paving stones, and many other products.
These granites might be used with sawn, sheared, or polished surfaces. Pegmatite: Photograph of a granite with very large crystals of orthoclase feldspar. Granites composed mainly of crystals over one centimeter in diameter are known as "pegmatites. Granitic rocks: This triangular diagram is a classification method for granitic rocks.
It is based upon the relative abundance of feldspars K-Na-Ca and quartz. Mafic elements are not considered. As an eruption ends, the basalt "scab" heals the wound in the crust, and the earth adds some new seafloor crust. Because the magma comes out of the earth and often into water it cools very quickly, and the minerals have very little opportunity to grow.
Basalt is commonly very fine grained , and it is nearly impossible to see individual minerals without magnification. Basalt is considered a mafic silicate rock.
Among other characteristics, mafic minerals and rocks are generally dark in color and high in specific gravity. This is in large part due to the amount of iron, magnesium, and several other relatively heavy elements which "contaminate" the silica and oxygen. But this heavy stuff really isn't happy near the surface, and will take any opportunity it can to head for deeper levels.
The trick is to heat the basalt back up again so it can melt and give the iron another shot at the core. It wants to be there, and heat is the key which unlocks the door. As it turns out , most of the ocean floor is basalt, and most of the continents are granite. Basaltic crust is dark and thin and heavy, while granite is light and accumulates into continent-sized rafts which bob about like corks in this "sea of basalt.
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