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  • Rhyolite

    Rhyolites in Carolina Slate Belt

    There are hundreds of different varieties of Rhyolite in the state, but the term Rhyolite is also used as a generic catch-all term for a lot of the meta-sedimentary materials.
    The southern end of the chain of mountains called the Uwharries they are part of the Carolina Slate Belt. Rhyolite is a fine-grained metamorphic igneous rock-an extrusive volcanic flow. In fact, you get two kinds of extrusives: rhyolitic flows or lava which is what this is, and volcanic ash, which forms the rhyolitic tuffs more common in the northern portion of the Uwharrie Mountains. One of the characteristics of Morrow Mountain rhyolite, is flow banding. Morrow Mountain rhyolite is so fine-grained that you can't see the mineral composition with your naked eye. Some rhyolite, however, has larger crystals in the ground mass that can be seen with the naked eye. It is called porphyritic, and the larger crystals are referred to as phenocrysts. The highest grade of rhyolite is extremely fine-grained and is close to obsidian.


    Exposed to the weather for a long period it can patina almost white !


    photos by Butch Wilson

    Flo banded:

    photo by Shartis


    Searching the fields of Northwest Indiana and Southwestern Michigan

  • #2
    Rhyolite in Missouri
    Posted by [JoshinMO]

    Rhyolite is a common volcanic rock in many parts of Missouri, occurring in many different grades and types:

    https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&u act=8&ved=0CB0QFjAA&url=https%3A%2F%2Fpages.wustl. edu%2Fmnh%2Fgeology-missour

    I found the large point in 2008:
    Click image for larger version

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    I keep six honest serving-men (they taught me all I knew); Their names are What and Why and When and How and Where and Who.

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