Gold Diamonds, also known as Big Yellow Jewels, are collectible items found in Luigi's Mansion worth 20,000,000G each, which is the highest value of any collectible in the game. They are significantly larger than Blue Diamonds and Red Diamonds.
Gold Diamonds are found in two spots. For the first one, Luigi must water a plant three times in the Boneyard (where Spooky resides): once when he first sees it, once after defeating Bogmire, and once after defeating Boolossus to make the now-flower bloom, revealing the diamond and several other treasures. The other can be found if Luigi captures all 50 Boos (not counting King Boo); the last Boo drops the Gold Diamond.
If Luigi captures the final Boo and saves, the Gold Diamond's location is saved as being on the ground. Therefore, if players do not save using a Toad after obtaining the Gold Diamond, it will be lost if the game is turned off or Luigi dies, since as the game is saved automatically after the final Boo is captured but before the Gold Diamond is obtained, the Gold Diamond will disappear and cannot be obtained again.
- Sinfield, George. Luigi's Mansion Player's Guide. Page 95.
- Bogenn, Tim. BradyGAMES Luigi's Mansion Official Strategy Guide. Page 11.