Having finally done this quest, I'm shocked I haven't done this earlier, The Stones of Barenziah.
Finding all of these then doing the immediate quest, will grant you a perk that you find more valuable stones in containers. Helpful for making money, when in dire need of it.
1. Eastmarch-Ansilvund Burial Chambers -Enter the Ansilvund Excavation and complete objective in the cave and it will be on the left part of the table in the back of the room of the Burial Chambers. Near the sword Ghostblade and Fjori's ghost.
13 The Reach-Markarth Treasury House-Next to the bed in the master bedroom.
21. Whiterun - Whiterun Hall of the Dead - Whiterun Catacombs -Found in a crypt. From the entrance make the first left, then right, down the ramp. From here it's on the immediate left.
Finding all of these then doing the immediate quest, will grant you a perk that you find more valuable stones in containers. Helpful for making money, when in dire need of it.
1. Eastmarch-Ansilvund Burial Chambers -Enter the Ansilvund Excavation and complete objective in the cave and it will be on the left part of the table in the back of the room of the Burial Chambers. Near the sword Ghostblade and Fjori's ghost.
2. Eastmarch-Stony Creek Cave-Off the main corridor follow a path on the right, inside thebandit wizard's cavern, on a table.
3. Eastmarch-Windhelm -House of Clan Shatter-Shield-Upstairs and in the first bedroom on the left. On the bookshelf.
4. Eastmarch-Windhelm -Palace of the Kings Upstairs-Accessible via the first door on the left upon entering the palace, it sits on a table in Wuunferth the Unliving's quarters at the end of the hall. On the table to the right.
5. Falkreath-Dark Brotherhood Sanctuary-On the dresser in Astrid's room during the quest With Friends Like These... or Destroy the Dark Brotherhood!
6. Falkreath-Pinewatch-Access the bandit sanctuary in Pinewatch by pressing the button downstairs, across from fireplace. Inside the sanctuary, to the right of a room containing a single bandit and several empty Draugr sarcophagi, there is another small room (to the right, behind a locked door) with a treasure chest. The stone is found on a shelf directly across from the chest.
7. Falkreath-Sunderstone Gorge-On the altar in front of the Word Wall.
8. Haafingar-Dainty Sload-On a table in the First Mate's quarters.
9. Haafingar-Reeking Cave-Beside the dead conjurer. This was originally found in the Thalmor Embassy but was later moved to Reeking Cave with the 1.4 patch.(For those who have to go back to get this one, you will be looking for an unmarked cave, north/north-west of the embassy.)
10. Haafingar-Solitude -Blue Palace-On the bedside table in Jarl Elisif's quarters.
11. Haafingar- Solitude Proudspire Manor-Sitting on a chest of drawers which itself sits on the left of the upstairs master bedroom. Can access rear entrance of Proudspire Manor with Solitude Fletcher's Key, in order to bypass paying 25,000 to own home.
12. The Reach-Dead Crone Rock-On a makeshift altar in front of the Word Wall at the top of the final tower.
14. The Reach-Markarth -Understone Keepwemer Museum-Once inside the museum, it can be found through a locked gate on left of the museum on a table in the right hand corner.
15. The Rift-Black Briar Lodge-In the upstairs master bedroom.
16. The Rift-Riften -Mistveil Keep Jarl's Chambers-In the Jarl's chambers, on the end table to the left of the bed in the master bedroom.
17. Whiterun-Dragonsreach Jarl's Quarters-In the Jarl's chambers, on the end table to the right of the bed.
18. Hjaalmarch-Rannveig's Fast-On a table just to the right of the prison's exit gate. The prison is accessed via a trapdoor in front of the chest that stands before the Word Wall.
19. Whiterun-Fellglow Keep-On a counter in the workshop at the top of the front foyer - between the arcane enchanter and the alchemy lab.
20. Whiterun-Jorrvaskr Living Quarters-Found in Kodlak Whitemane's bedroom.21. Whiterun - Whiterun Hall of the Dead - Whiterun Catacombs -Found in a crypt. From the entrance make the first left, then right, down the ramp. From here it's on the immediate left.
22. Winterhold- College of Winterhold Arch-Mage's Quarters-On a shelf in the Arch-Mage's Quarters. To the left of the bed, under a wolf's head mounted on the wall. Becomes accessible during "Under Saarthal".
23. Winterhold-Hob's Fall Cave-Just after crossing the bridge, before you get to an area with a sacrificial table and enchantment table, take the path to the left and down into an area with an alchemy bench. The stone is located here on a shelf.
24. Winterhold- Yngvild - Yngvild Throne Room-Found on the desk in this last room, next to the final journal of Arondil.