Actually, Terramap can count ores, or mostly any kind of block.
if you select an ore from the block list, then "highlight all", in the bottom right of the screen it will say "Highlighted x out of 5040000 blocks in x seconds"
If an chest has an ore or other block, it will count it too, adding 4 blocks for each chest with the selected items. Certain blocks like demon altars or statues can be counted too, is just that each one equals to 6 blocks.
however, there are some things it can find, only show, like life crystals or gems that are embed in stone (but it can count the gems that are placed in stone, or stored in chests.