you're going to have to make it easier for people to help you! It's not even clear if you're talking about a Ducati, although that can probably be implied
Get a file. File off a small section of your wheel rim. Collect powder. Heat. If it burns instantaneously with a blinding white flame - magnesium alloy. If not, Aluminium Alloy. * not scientifically proven. Based on Chemistry O Level 1978.
OK.... Assuming that they are 748/9*6 5 spoke wheels: Magnesium Alloy: rear wheel generally* has small diagonal brace "framework" inside the back-side (viewed from left hand side) of the spokes. * early race wheel has no bracing inside the spokes Front and rear spokes are "smooth" externally with no ribs or seams. Aluminium Alloy: front and rear have a casting feature on the outside of the spokes. No bracing inside spokes. AFAIK.
You are welcome. Can you let us know the answer so that the variously OCD/inquisitive types can mark the item as "closed". Cheers.