Experts will tell you that the kasauti stone is a time honored and reliable way to test the quality and purity of gold. This stone is of professional grade quality, and measures 4" x 2" x 1/4". Simply rub the gold on the stone, and then apply the gold testing acid (not included) to see the reaction. These is a specific acid to determine different purity levels of the gold. * 4" X 2" X 1/4" * Black Stone * Tests Quality Of Gold * Weighs 3.8 Oz * Professional Quality