We got this at an auction of an old rock shop. It was in a big dusty box marked optical quartz but after examining it, we are pretty darn sure it's fused quartz. It was probably originally intended for use in radios or watches. From way back in the olden days! It's a vintage rock. It is colorless, and does have inclusions and veils here and there. It makes great, cheap, practice rough or just a good conversation piece. Supposed to be softer then hydrothermal and take a good polish. What is fused quartz? Click here for the wiki article.