Well, Lakeview has that iron ore vein just beside the horse carriage. Sylgja will even mine it actually, but the trade-off is that you can't build a west wing extension in order for this to happen.
EDIT: Sorry, I meant east wing (kitchen/library/armory)
I built my library in Lakeview and the iron ore vein is still there.. or is there another one which disappears? The one which is there just slightly beyond the workbenches if you exit the main door of the house. My steward spends a lot of time pretending to mine the rock which is now empty.
If you're on the PC, you can install a Sylgja follower mod, arm her with good weapons, and then leave her be - the spiders wouldn't be able to touch her. You could technically just console her a weapon and a few levels and she'll still be safe. The spiders don't attack if you don't enter the mine, in any case. Once you enter, they still don't attack unless you're detected, at which point all hell breaks loose. The only casualty I have in the mine is the rude guy who mines at the bottom. Sylgja and the orc, both who mine at the top floor, never get hurt because the spiders come toward me, and I kill them fast enough. The spiders at the bottom eventually got the guy down there because he hit them and drew aggro from them before I could get down there.