What is my pizza cutter's handle made from, and how do I stop it from staining everything it touches? A while back, I bought an ordinary-looking pizza cutter with a dull grey handle.  However, I soon found out the hard way that the handle is made from some weird metal or alloy that reacts with water, staining everything it touches black:



"Water" here includes even slightly moist or sweaty hands, making this a real pain to use.  What is this stuff and how do I stop it from staining?  And for extra credit, why on earth would you make a hand-held kitchen utensil from it?!
Mystery solved!  At Catija's prompting, I managed to dig up the cutter on the website of the shop I bought it from, the Chef's Hat in Melbourne, Australia:



CUTTER PIZZA W/ALUM HANDLE 95MM S/ST ($6.60)

So turns out the handle is aluminum (aluminium), which can be discolored black if the alloy is not dishwasher-safe, which this clearly wasn't.  Time to ask a new question about what, if anything, I can do to fix it!