This is an unusually fine slab of AL/TN paint Rock Agate. The end cut is suitable for cabbing or for display as is. The end with the complete fortification appears quite solid and is thick enough for cabbing, and would make a great collector slab. The other half or so is cracked but probably would produce a nice cab or two. I believe it would hold together in flat lap polishing.
The size can be seen on the one inch grid, thickness from about 5 up to 14-15 mm.