G I A N T  S I Z E 

Genuine , natural obsidian, smooth for the best quality test results. Don't settle for glass. This is the smoothest natural stone with high contrast and minimal gold loss.

Jet black, super high contrast natural obsidian is the time tested BEST material to use to easily test gold. Its smooth surface prevents excessive gold loss when testing. Do not use glass, as it does not work correctly with acids.