Ok, a method you may or may not have the materials to do: Pulverize a small sample. Boil for a couple minutes in dilute nitric acid. When solution is cold, decant off and add a pinch of common table salt and stir. If the solution turns milky white and settles to the bottom, drain acid and wash with distilled water. Boil for a couple minutes in distilled water. Anything remaining is PROBABLY silver.