This is amazingly bright and beautiful glass. Just hold the leads of the giant 10mm clean lens UV across the included CR2032 coin battery (long lead on + terminal) and you will be amazed at the brilliant green glow. These are larger opaque chunks that may have darker swirls in them. Minimum size 0.75" long x 0.25" (of course they will be irregular in shape and height varies from very thin to larger heights). The glass is slightly radioactive and can be measured by Geiger counters that use sensitive tubes such as CTS-5, SBT-11A, etc. Remember you get an opaque Uranium Vaseline class cullet, a giant 10mm UV LED & C2032 in the package.