GTE 3''x6'' Large Test Stone for Jewelry Testing - Perfect for Gold, Silver, and Platinum This LARGE 3''x6'' GTE Test Stone is a must-have tool for testing the purity and karat value of gold, silver, platinum, and other precious metals. Designed for use with testing acids, it's the perfect companion for determining the authenticity of jewelry, scrap, coins, bars, and more! Easy to Use: Simply scratch the test stone with your jewelry and apply a drop of acid to the stone to observe the results. Note: Testing acids are sold separately. Durable and Long-Lasting: Each stone allows for over 1,000 tests. Easy to clean using acid neutralizer or a simple baking soda and water rinse between uses. Great for Everyone Who Deals with Precious Metals: Ideal for investors, collectors, and jewelers who work with gold, silver, and platinum. Our goal is to make jewelry testing FUN, FAST, and EASY! This 2-Piece Kit Includes: GTE 3''x6'' Test Stone with a rubber backing for a non-slip surface during testing. Instruction Booklet with an easy-to-follow color chart for accurate results. Make jewelry testing quick, simple, and reliable with this GTE Test Stone. Perfect for ensuring the value and purity of your precious metals.