Metal zipper tags and belt buckles melt very easily and can be melted by heating it in the stove for 5 minutes. But other metals like aluminium refuse to melt even after hours.
If you leave it overnight, it dissolves pretty well in vinegar. I am sure they are made of metal, as I've melted it and cast some metal cookies. The metal is denser than aluminium, shiny when molten and cast, but surface tarnishes after 1-2 hours. I'm guessing it is some type of a zinc alloy.
The metal of the zip tag has the following characterisitics:
- tarnishes into a dark gray
- does not colour a flame in odd colours (like red , crimson , green etc.)
- malleable (easy to bend a 5 mm thick square just by using leverage of hands and a surface to press down on)
- brittle if bent a couple of times.
- melts in a few minutes
So, what alloy or metal are they made of?