There are a number of folk "tests" that are supposed to tell you whether a mushroom is poisonous or not. For example, a mushroom is supposed to be poisonous if:
NONE OF THESE TESTS WORKS - - AT ALL!
First of all, I don't know of ANY mushroom that will turn silver black - - in fact, I don't know of any food whatsoever that will turn silver black.
The two groups of mushrooms that cause 90% of the fatalities in USA (Amanita virosa and Amanita phalloides) will not turn silver black, and they also can be peeled. They have a pleasant (not bitter, not burning) taste both before and after cooking.
The mushroom that single-handedly causes 45% of all mushroom poisonings (it's a thrower-upper) in the USA (Chlorophyllum molybdites) also passes all of these tests. If even has little wispy things on the cap that you can peel off to reassure yourself about that particular test.
