For future reference, U can gently tap or grind a stone against ur tooth or another piece of glass, like a tea glass, magnifying glass or eye glass lens & U'll notice a distinct 'cold chills' feeling & sound if the stone is glass, like fingernails on a chalk board! If ur still not sure, due to these stones being small, practice with larger things, like glass marble or fingernail polish bottle + the plastic bottle lid so U can experience the difference ;-) ThankU for ur resply & good luck as a new Listian! :)