How much does a pallet of durock 1/4" cement board weigh?
1710 lbs, 1.9 psf for each 1/4" 3'x5' sheet. You're correct about 60 pieces per unit. 
Durock Spec Sheet

Showing my math:

3' x 5' = 15 square feet

15 square feet x 1.9 pounds per square feet = 28.5 pounds per sheet

28.5 pounds per sheet x 60 sheets per unit = 1710 pounds