'Stalagmite' Pony Creek Thunderegg

Unusual not because it is hollow and with just a thin layer of dark agate, but because of the strange growth inside the hollow. I am not sure what it is (though obviously not a true stalagmite) but it makes this a very special and striking thunderegg. The matrix is very elegant as well. This is an image taken with a scanner.

from the old "PONY CREEK" area on Ochs Ranch in Eastern Oregon