How much does a 6 x 6 ceramic tile weigh?

Not sure how exact you neeed to be, but the thickness & the density would be unknowns from your question & they will both impact the answer.

A 6X6 wall tile will be less than floor tile & thick tile likely more than thinner. But if you use 8-10 ounces per 6X6 floor tile you will be very close. Add thinset & grout & still more variables crop up.

That is if it is really ceramic, travertine, porcelain or Saltillo would all be different too.