Features 1、This touchstone is used to verify the gold content in items 2、Apply a drop acid test on touchstone, real gold will stay on the touchstone, fake one will be dissolved or oxidized to blue 3、This solution works for testing any gold which you believe to be 10K, 14K, 18K, 22-24K, silver, and platinum pure 4、Acid changes color based on purity. Very easy to use 5、Ideal for testing jewelry, coins, antique gold, silver, platinum collectibles Specification Features: 1. This touchstone is used to verify the gold content in items. 2. Apply a drop acid test on touchstone, real gold will stay on the touchstone, fake one will be dissolved or oxidized to blue. 3. This solution works for testing any gold which you believe to be 10K, 14K, 18K, 22-24K, silver, and platinum pure. 4. Acid changes color based on purity. Very easy to use. 5. Ideal for testing jewelry, coins, antique gold, silver, platinum collectibles. Specification: Condition: 100% Brand New Item Type: Touchstone Material: Stone Color: As pictures shown Size: S, L (optional) Size Length Width S 7.6cm / 3in 3.8cm / 1.5in L 9.9cm / 3.9in 5.2cm / 2in Package list: 1 * Touchstone Package List