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
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
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