So, basically it's a flat volcano, surrounded by a couple of murky pools (one of them is currently flowing down the volcano mouth, revealing the great magma sea and blue stuff, along with other minerals), a small hill and a little mountain.
Except the blue stuff, I've seen only nickel so far. Also a good variety of gems is present.
It's crucial to dig for caverns to find a stable water source, cause murky pools are not to be trusted, you know =)

PS the volcano is in the south.