Cartwheeling. When one rotates a coin in direct light, the luster flashes around the coin giving the illusion of a "cartwheel".
Cartwheeling is the effect you get from holding a coin so that when you tilt the coin the, the light source rotates around the coin, like the spoke of a wheel. It happens only from freshly minted coins with no wear: the metal molecules flow out from the center of the coin in radiating rays. I just learned about this phenomenon recently. The name comes from silver dollars, so I understand. I can readily see the effect in my America The Beautiful Quarter collection. I hope this helps. Good luck.