All I can find is almonds with the skins on also. But they have always worked fine for me. I soak them in the salt water and then dry them at 150* in my electric oven. Never any black spots. The only thing that comes to mind is that maybe they are reacting to the metal in your baking sheet. I've used both stainless steel and one with a non-stick coating with success. Is your baking sheet aluminum or some other reactive metal? Just a thought.