Luigi finds a Blue Stone.
Stones, also called Jewels, are valuable collectibles or treasures found in Luigi's Mansion. There are three different colors of Stones: Blue (500,000G each), Green (800,000G), and Red (1,000,000G). Ten of each color can be found in the Mansion, totaling 23,000,000G. To find them all, Luigi should water all the plants he can find, examine some objects such as buckets, gutters and gold chandeliers, catch Speedy Spirits, and light up all the rooms in the mansion except for the 3rd and Basement floor hallways.
Luigi also found stones in the game Mario is Missing!. They were stolen from the Obelisk Monument in Buenos Aires and the Great Wall of China in Beijing by Koopa Troopas, and Luigi had to return them to the monuments.