No Stone Unturned (Skyrim)

Quick walkthrough

 * 1) Find an Unusual Gem.
 * 2) Bring the gem to Maul.
 * 3) *If already a member of the Thieves Guild, skip to Step 3.
 * 4) The Dragonborn must bring an Unusual Gem to Vex in the Thieves Guild, who will explain that it is one of the Stones of Barenziah. She will also say that it is not worth much by itself, and that there are twenty-four of these stones.
 * 5) Collect any remaining stones and return to Vex.
 * 6) After the Dragonborn returns with the gems, Vex will ask for the recovery of the Crown of Barenziah from Tolvald's Cave.

Find an Unusual Gem
Unusual Gems can be found all over Skyrim. Once at least one is discovered, the quest will be eligible to be started.

Not a Thieves' Guild Member
Once a gem is found, travel to Riften. There, the Nord thief Maul can be met. After speaking to him, he will tell you what he knows of the gem, and request for you to speak to Vex in order to find out what the gem is worth. He will also state that Vex can only be spoken to if one is a member of the Thieves' Guild. If you urge him for more information on the guild, he will direct you to Brynjolf in the Riften Marketplace, or if the time is night, the The Bee and Barb. Speaking to Brynjolf will begin "A Chance Arrangement". Once access to The Ragged Flagon has been gained, Vex can be spoken to. She will explain to you that the gem is one of twenty-four total stones that were pried from the crown of Queen Barenziah by a thief in an attempt to cover his tracks, and that only the complete set of the 24 stones would be worth anything. The new set of such information begins the objective to seek out the rest of the valuables.

Already a Thieves' Guild Member
If one is already a member of the Thieves' Guild, Vex can be spoken to immediately. She can easily be found in The Ragged Flagon, and will tell you that it is one of twenty-four stones that were stolen from the crown of Queen Barenziah by a known thief in an effort to hide his tracks. She also mentions that only the complete set of the twenty-four stones would be worth anything notable. This explanation begins the objective to seek out the rest of the gems.

Finding the rest of the Stones
The following are locations for every Stone of Barenziah:

Recover the Crown of Barenziah
Once Vex is shown the full set of the twenty-four stones, she tasks you with traveling to Tolvald's Cave to retrieve the Crown of Barenziah. The cave has three levels and is filled with many Falmer, as well as various fungi. Upon entering the cave, there is a Frost Troll and an apprentice level chest behind the pillar to the left. One can go down the cave and face another two Frost Trolls. Go through the door at the end of the path. There is a trapped chest, coin purse, and gold ore on the table directly ahead, and then three Falmer will appear. Follow the path to either direction, as both will lead the same way, and once one reaches the top, there will be another two Falmer in the room with an Alchemy Lab. Continue down the path until reach three Falmer are reached. A chest to the left of the shelters will also be present, but one will also proceed to fight a Frostbite Spider. Keep to the left to find and unlock an Adept chest. Then, one will encounter another two Falmer near the fire. Open the gate to the hut to search another chest. Continue down the path to Tolvald's Gap.

Upon entering, several Falmer and Skeevers will be faced in combat. Afterward, take the bridge to the right and inside a hut is another chest, while within the room is a bounty of fungi. Exit the room and follow the stream to the south. There will be a couple of Frostbite Spiders and Falmer. Follow the stream to the left and take a right up the path. If one decides to open the gate to the right, there will be a few Chaurus Hunters. Otherwise, head up the left side of the next room to unlock an Adept Chest and continue down the path. Kill the Falmer and upon reaching the next room, but do not jump down, as the position will return one to a previous spot. Guide to the right, down the tunnel, and upstream to Tolvald's Crossing.

Upon entrance, one will be greeted by a Falmer Warmonger on the bridge. Upon crossing the bridge, continuing forward will lead someone to a chest, but also to the crown. Turn back and take the first path to the right which is equipped with a Trip Wire. There is a chest ahead on the right, a coin purse directly ahead with a bunch of books, and a few Falmer up the path to the left. Make a U-turn up the path to gain access to a Master Chest. Turn back and follow the path to a hut with a chest inside, and then continue through the gate. The next room will have a table with bones and random loot on top of it. As one continues upward, they ought to kill the Falmer, and search the Chest to the right. The next room has Chaurus Hunters and Falmer Warmongers. Open the gate on the other side of the bridge and continue forward. Keep left and cross the pipes to reach Tolvald's Cave. In the event that one did not get the crown, they can easily drop down the falls cautiously and retreat left.

Down the pathway, there will be a Pull Chain to the left that will open the stone wall. Continue straight ahead and exit to Skyrim.

After giving the Crown to Vex, it will be placed as a trophy alongside the rest of the Larceny Targets, and the individual will be rewarded with the effect Prowler's Profit.

Bugs

 * If the Dragonborn is already a member of the Thieves Guild and has shown the gem to Vex, and then talks to Maul in Riften about the stone, he will suggest becoming a member of the Thieves Guild, adding a quest objective to join the Thieves Guild. While this objective cannot be cleared, it will not prevent the quest from being completed.
 * If the Dragonborn already possesses all twenty-four gems when talking to Vex for the first time, the game will not recognize them, and the quest will be uncompletable. Collect twenty-three or fewer gems before talking to her to prevent this bug.
 * This bug has reportedly been fixed by patch 1.9.
 * Sometimes the quest objective will count extra stones that have not been collected (i.e., saying 10/24 Stones have been collected when the Dragonborn only has 8). The quest can be completed when the objective says 24/24, even if some stones have not been collected yet.
 * Fixes for this quest if it becomes bugged or uncompletable. Note that these may not update the journal, but will unlock the appropriate responses from Vex. On the console type the following commands:
 * To initiate the search for the crown (if stones are missing)


 * If Vex won't talk despite having all the stones:


 * If the Crown is missing:


 * To remove the quest from the journal:

Keinen Zacken aus der Krone brechen No quede piedra sin remover Tous les moyens sont bons Заглянуть под каждый камень