There are 51 Sapphires in the picture
if you want to know how many is hidden ... well that is impossible since hidden means to be kept out of site hence we would not see them and you could change the answer to what ever you wished
o well i guess for the number of "hidden" saphs i will go with 2000 buried underground LOL
if you mean obscure then i say 10 (either its bad lighting or just partially covered by the priestess legs)