Only if you are doing it in an attempt to profit or gain... so no, burn away.
Edit:Title 18 United States Code, Section 331
Whoever fraudulently alters, defaces, mutilates, impairs, diminishes,
falsifies, scales, or lightens any of the coins coined at the mints of
the United States, or any foreign coins which are by law made current
or are in actual use or circulation as money within the United States; or
Whoever fraudulently possesses, passes, utters, publishes, or sells,
or attempts to pass, utter, publish, or sell, or brings into the
United States, any such coin, knowing the same to be altered, defaced,
mutilated, impaired, diminished, falsified, scaled, or lightened -
Shall be fined under this title or imprisoned not more than five
years, or both