I went to the Uwharrie National Forest today to do some scouting for trail building for mountainbiking. (One of my other passions)
Anyhoo, they did some logging on one of the trails called Supertree. In cutting the road bed for the logging equipment they unearthed some rhyolite ( I'm pretty sure it's rhyolite). As far as I can tell you can remove minerals from Uwharrie. You can even still stake a gold claim in some parts.
If you're a knapper and are looking for some material to work it may be worth a trip to Uwharrie just off 24/27 in Montgomery County, NC near the Lake Tillery dam. Vehicle access is limited. Take your backpack or wheelbarrow.
If this isn't the right place for this Mods, please accept my apologies.
A small sample.