![Natural Obsidian Test Stone-Metal Verifiers, Testing Kits & Acids-Transline-StampPhenom](http://stampphenom.com/cdn/shop/products/resize_3fc54868-aa09-43d2-a502-3643acf340b7_{width}x.jpg?v=1606800348)
Natural obsidian test stones give precise readings when testing for gold purity. Obsidian is a volcanic glass produced when lava becomes cold. It is been used for years to make the sharpest knives. Obsidian test stones, on the contrary to rougher test stones, have a perfectly smooth surface that provides more consistent and reliable readings. Transline#: gt35. Size: 5x2x1/2. Color: Black. Sold Individually. Case Qty: 1 .