Is this rhyolite...?

[BabaORiley]

I found this a while back in a field in N'Eastern Illinois. Its about the size of a 2lb chuck roast. It looks just like the rhyolite described in an Illinois artifact book I have but I saw another post where the rhyolite looked much different in color.

[Flyjunkie]

Not 100% , but it does resemble the Fremont Butte Rhyolite one can find around various locations in the western Antelope Valley here in So Cal. the 'Butte Rhyolite' was a common lithic material for the Antelope valley and adjoining areas. it was quarried all around the base of the Fremont Buttes (you can still see the eroded quarry pits in some areas there). It was trade far and wide in ancient Southern California and the southwest corner of the Great Basin.

I don't know Rhyolite as well as i do our other local lithic materials.. Wish i did, but last search for information online provided little information.. time for another search I guess

But the looks of that stone you posted reminds me of our local Rhyolite, so on my limited knowledge I will say it is Rhyolite...

[kayakaddict]

There are so many shades of rhyolite (and argillite) and of course when it weathers it changes. A real comprehensive guide would be helpful but I don't think there is one.

[Hoss]

I think it is Porphyry

[Tam]

How do you guys even know this !!! I keep reading but dang