The Lord’s Touchstone
Howard W. Hunter October 1986 Saturday Afternoon Session
In ancient times, one test of the purity of gold was performed with a smooth, black, siliceous stone called a touchstone. When rubbed across the touchstone, the gold produced a streak or mark on its surface. The goldsmith matched this mark to a color on his chart of graded colors. The mark was redder as the amount of copper or alloy increased or yellower as the percentage of gold increased. This process showed quite accurately the purity of the gold.