This is a terminated piece of Yellow Apatite from Cerro Do Mercado, Durango, Mexico. This piece has a very vibrant yellow color with tons of rainbows inside. You see them best from the side faces, and some of them run the whole length of the crystal.
Apatite has several colors it can be, including blue, pink, yellow, and clear. Mexico produces most of the yellow apatite out there and has the best color for them.