These EASY to use genuine lot of 4 GTE Acid Scratch Test Stones are a convenient tool to use with testing acids to determine the karat value and purity of Gold, and Silver Jewelry, scrap, bars, coins, and much more! Simply scratch the test stone with your jewelry and apply a drop of the acid to the stone and watch the results appear! *Our goal is to make testing your jewelry FUN, FAST, and EASY! *Each stone will allow for over 1000 tests! Simply clean with acid neutralizer or a baking soda/water rinse between testing. *A MUST-HAVE for anyone who invests in gold, silver, or platinum! This 5 Piece kit includes: - GTE Black 3''x6" Test Stone , GTE Black 2''x4'' Test Stone, GTE Black 2''x2'' Test Stone, and GTE White 2''x2'' Test Stone. Each with rubber backing to ensure non-slip desktop testing! - Easy to follow instruction booklet with color chart! (Note: Testing acids sold separately)