Answer:
1. Magnetic Properties
Gold in its pure form is not magnetic. If it is placed in a magnetic field, it will magnetize a bit only as long as it is still in the field.
Pyrite on the other hand would stick to a magnet because of its high iron content; same with chalcopyrite.
2. Physical Properties
Gold is highly malleable and ductile. While pyrite and chalcopyrite are both brittle, however, pyrite is harder than chalcopyrite. However, a sample of chalcopyrite would be easily scratched with a nail while pyrite won't.
3. Color
Although, the three might possess almost the same color confusing prospectors, a simple shade test will set them apart. Gold will remain the same even in bright sunlight and in a shade however, pyrite and chalcopyrite change color when viewed in shade. Pyrite and chalcopyrite will look brassy dull yellow or dark in shade.
4. Weight
When flaky and spread on a pan of water, gold sinks to the bottom while pyrite and chalcopyrite floats.
5. Chemical Test
Using Nitric acid, place a few drops on each samples, pyrite and chalcopyrite would definately change color usually to black while gold remains the same.