According to the UESP Wiki page for Skyrim Mining, unclearable mines have their ore repopulated every 10 game days, while clearable mined repopulate every 30 game days.

Now... does this account for only the ore, or for everything in the mine? Are the contents of sacks and chests repopulated as well, or is it just the ore veins? What about the mine inhabitants? Are they restored after a certain period as well?

An example is the Emberhsard Mine, located between Helgen and Riverwood. After clearing the mine, the mine is marked on the map as "cleared". Now... if I drop items into one of the chests inside the mine, are the chests's contents "safe" or could they be lost? And will I need to fight my way back inside after a few game days?

http://www.uesp.net/wiki/Skyrim:Embershard_Mine

Almost everything will respawn. Contents of sacks and chests will repopulate, as well as the ore veins. The inhabitants will respawn as well. All things in Skyrim follow either 10 day or 30 day respawn rule. There are some quest related dungeons that do not respawn at all.

If you clear Embershard Mine and put something in a chest, it's safe as long as you return within 30 days. If you do not return within 30 days, you will lose everything in the chest, and almost everything will respawn.

I usually can't mine the ore veins when I return to the mine for the first time after a while (the "press XY to mine ore" popup just doesn't show up), so I have to wait another bit and return later again.

But I am not sure if that is the side-effect of one of the mods that I'm playing with.

It may e that you just hadn't given the mine enough time to respawn, Lytha.

(Personal sidenote: Your identifying graphic looks almost exactly like a tabby cat I used to have. )

Sometimes respawning breaks and things that should respawn do not. But some people reported being able to fix this by revisiting the area couple of times. I have seen it as well in my games that some areas that should respawn do not. Someone mentioned that if you clear an area and revisit between 2 and 9 days, respawning breaks. I have not tested this myself, though.

I wouldn't say that revisiting breaks the timers. It's more accurate to say that revisiting resets the timers. As was mentioned above, ore veins are on a 10-day timer, so if Lytha revisits that mine once every nine days, the ore will never respawn.

It was the same in Oblivion. It just wasn't as noticable in Oblivion because that game had a three-day timer.

I was talking about respawning breaking the timer and it never respawning again no matter how long you wait. I have seen this behavior myself, and other people reported it as well. Apparently it's more common among people who do not fast travel. There is also a mention of it on the UESP wiki: http://www.uesp.net/wiki/Skyrim_talk:Respawning

No, I gave the mine more than 2 ingame months before I visited it again. I first noticed it with Stony Creek cave and the moonstone veins inside (every NPC in the Windhelm area seemed to send me into that place...) and with the "honestly, we just mine iron here, not ebony" near Shor's Stone. On the 2nd visit in such a place, when enough time has passed for the enemies to respawn, the ore vein has somehow lost the interactive object status. On the next visit afterwards, the ore veins are back to normal.


(The avatar is my tomcat Julian. He's awesome. )

Give it a few weeks - real time - and go back to Helgen.

Eventually, bandits take over and keep returning.