Any place where there are valuable minerals.
in the mine
Hobgoblin Mine is the best place for non-members - 8 rock and Abandoned Mine sis the best place for members - 13 rocks
The best place to mine silver ore is Al kharid mine as this requires no quests.
If you have 66 magic than the magic guild is the best place
deadmines...
open pit mining
Living Rock Caverns
barb village
For non-members, the ONLY place to mine it is in the wilderness level 40 or so, a rather dangerous place to go (mainly due to the revenants).
Living Rock Caverns
At the base of a paleo waterfall.
In a mine eg a gold mine a diamond mine ect...