Onyx or Agate?

This rock looks like it could be a type of chalcedony, specifically agate or onyx. The translucent to semi-translucent nature, the banding, and the smooth, polished surface are characteristic of these types of rocks. Agates often have layers or bands of different colors, and onyx is known for its parallel bands. The coloration in your rock, with its light tones and some darker inclusions, fits well within the range of agate or onyx variations.