Mining

Mining is an action in performed at ore veins using a Pickaxe. Ore veins produce their respective ores and possibly a precious gem.

Ore veins generally replenish their ores after about a month (in-game) if the area is marked as "cleared". Otherwise, it replenishes in 10 days. Some veins (e.g. Ebony) respawn sooner, or later than the one month. Each vein, regardless of ore type, will yield three pieces of ore, and at most two precious gems.

In rare cases, some entire mines or locations will NOT respawn their ores at all. There is no known fix or cause for this.

Quantity
All ore veins contain 3 pieces of ore, and possibly some gems. A popular misconception is that if continually mining, the player only receives 2 ore from each vein. When the player hits the ore 9 times, you DO receive 3 ore per vein, however the game only displays the message twice (1st & 3rd Ores). The sound for receiving an ore still plays on the 6th hit, and if you check your inventory you will find that you have 3 more ore. Note: If you receive a precious gem (Garnet, Ruby, etc.) on the 6th hit it will display the message for the gem, but not the ore.

Ore
There are 9 different types of ore that can be mined in Skyrim.

Ore Veins are all across the world of Skyrim from simple mines to the tops of mountains. You can identify that they are minable by the different colored striations that stand out in the typical grey rocks that dominate the landscape of Skyrim. Environmental conditions can make it somewhat difficult to spot and identify a node. When a vein is mined completely, it will lose the colored striations associated to that mineral type.

Depending on your style of game play, travel may increase or decrease your chances of encountering world mining nodes. Players that use fast traveling will be less likely to encounter nodes than a player that travels via horse back or on foot.

Locations
Locations specific to each ore are noted on the pages below:
 * Corundum Ore
 * Ebony Ore
 * Geode Vein
 * Gold Ore
 * Iron Ore
 * Malachite Ore
 * Moonstone Ore
 * Orichalcum Ore
 * Quicksilver Ore
 * Silver Ore
 * Shellbug

Ore vein reference
Each vein has its own distinctive color and pattern, which disappears after the node has been mined and the rock returns to its normal gray color.

Trivia

 * You can also mine by equipping your pickaxe in one hand and then hit the vein. It requires as much hits as it would if you activated the vein, but this goes faster and you can react faster if you are attacked.
 * Another possible way of mining faster is using the Elemental Fury shout prior to manually hitting the ore with a pickaxe.
 * During replenish time, the vein may regain its colored striations, but is unable to be mined. This is just a way to display progression of replenishment, and is no cause for worry.
 * Some NPCs such as Irgnir, a female Nord and Fruki, another female Nord, will work in the mine and very often get in the players way. In their scripts they will arbitrarily mine various ore deposits or bare rocks, and this will cause a glitch. Killing these NPCs has no bearing on the storyline or game progress. Their dialogue options are short and simple and they offer no assistance and no loot, and carry no armour. Killing them will allow free uninterrupted access to everything within the mine.
 * In the Markarth prison, Cidhna Mine, if you mine a ore, you complete your jail sentence.

Bugs

 * Sometimes there is a glitch where an ore vein will regain its coloring as replenished but no dialogue for mining appears. To fix this, find a house/cave/mine nearby, enter it, exit it (if you're already in a mine, simply exit it then re-enter it) then go back to the ore vein and the dialogue for mining will appear. Also, rarely, this may be fixed by equipping the pickaxe and "attacking" the ore vein.
 * On some occasions when the bug above occurs, if you leave the mine and go back in, you will still be unable to mine from a few deposits. This can be very easily rectified by leaving the mine, standing by the entrance and waiting for 24 hours.
 * When the player starts to mine, they will continually dig, but no messages for receiving the ore will be displayed and the player will continue to mine unless interrupted. This also can be fixed by equipping the pickaxe and manually "attack" the ore vein. This glitch is caused by other NPC characters in the area carrying out their programming and moving to mine the ore vein before you got there. A simple fix is to stop mining, and then immediately start again.
 * When the message in the top left of the screen displays "ore received", it will only show twice, but you will have received three (all veins yield three ore). However, the "ore received" sound will occur all three times. You can equip the pickaxe and "attack" the ore, this will show all 3 ores that you receive.
 * If you equip a pickaxe and, rather than "attacking" the ore vein to mine, simply activate the vein to mine normally, the pickaxe will stay equipped on your belt, but you will use a "second" one to mine with. You do not keep this second pickaxe - the glitch is purely visual.
 * Occasionally, hitting the activate key a second time before mining starts will cause mining to halt after a moment with no ores gained. The vein will still appear ready for mining complete with contextual activate command, but pressing activate again will do nothing. (Conjecture: the error may resolve itself when the vein replenishes) (You can gain the ores by equipping your pickaxe and "attacking" the ore vine)
 * Occasionally, the player will only hit the ore once and not gain any ore. This is easily solved by hitting the vein with a pick, but the option to mine will still be there