How is Quartzite Made?

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    What Is Quartzite?

    • Quartzite falls into the classification of a metamorphic rock. Its original material, sandstone in this case, has been altered by pressure and heat that transforms it into quartzite. Buried deep inside the earth the sandstone adapts to the change in conditions by altering its texture and composition. Sandstone recrystallizes, fusing itself together and becoming a strong, granular rock formation. The composition of the sandstone never changes, its chemistry stays the same. However, it fuses together from the heat being supplied and is pressured into a solid form instead of the more singular grains of sandstone we see at the beach.

    Quartzite Characteristics

    • Quartzite registers as a 7 on the Mohs hardness scale. Quartzite can be found in varying shades of red and tinges of pink because of iron oxide that becomes mixed in with the sandstone. Other impurities can make their way in to the mix causing various color changes but most quartzite is found as a white to grey color.

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    Forming Quartzite

    • Quartzite is formed through two types of metamorphism: contact and Barrovian. It can be formed by one of the processes or the other but it can also be formed by the combination of the two. Barrovian metamorphism happens during large earth events that create mountains and move sedimentary rock in a big way. During Barrovian metamorphosis the rock is squeezed, pushed and crushed together with very strong pressure. During this process, quartzite can become banded in layers of dark and light minerals. This banding places layers of biotite and amphibole, which are dark minerals, with quartz and feldspar, the lighter colored minerals. This is called a Gneiss texture or mineral banding.

    Contact Metamorphism

    • The second method that forms quartzite is the contact process. Contact metamorphosis happens in the area that surrounds a heat oriented or igneous event. The rock becomes baked in the heat but does not experience any pressure during the process. This causes the sandstone to become granular in texture and fuse by melting and not by force. Contact metamorphosis can happen right alongside Barrovian formations if there is a heat source during the process or by the combination of both. This is where it becomes difficult to separate the methods. It is far easier to identify a contact created quartzite if it occurs at the site of small igneous events.

    Finding Quartzite

    • Quartzite in the U.S. is found in Southern Idaho, Utah, Wisconsin, central Texas, eastern South Dakota, southwest Minnesota and in the Appalachian Mountains. Resistant ridges in many mountain ranges contain quartzite. Resistant refers to the fact that the ridges are obviously made of materials that are more resistant to destruction by nature. The mountains have been formed by the movement of the Earth’s plates or tectonic events where Barrovian metamorphosis takes place.

     

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