There are six collectible gems on each floor in Luigi’s Mansion 3. In this guide, I’ll show you where to find all six gems on the 15F floor and tell you how to get your hands on them. Please note that some of the gems will appear clear rather than coloured in the screenshots seen below, this is because I had already collected them during my playthrough before creating this guide.
Gem #1 – Lounge
In the Lounge, look at the rug in the middle and you’ll notice that there’s a small table at either side of it. Stand on one table with Luigi and stand on the other with Gooigi and the Green Gem will rise up from beneath the rug.
Gem #2 – Lounge
In the top left hand side of the Lounge you’ll see a pipe in the wall. Use Gooigi to slip through this pipe and you’ll come out on top of the elevator. Drop down the gap in the wall behind the centre of the elevator and you’ll find the Purple Gem.
Gem #3 – Hallway
As soon as you get into the Hallway, run to the left and you’ll find a picture of King Boo with a shadow being cast over it by a statue which sits just in front of it. Use your vacuum to rotate the statue until its shadow matches the shape of King Boo, which will open up the picture to reveal a picture of Luigi behind. Rotate the statue again until the shadow matches the shape of Luigi and the second picture will open up to grant you the Clear Gem.
Gem #4 – Library
Go into the library and head down the stairs. On the bottom floor, run to the top left corner and you’ll find a little hidden room behind the shelves. Here, use your vacuum to suck up the large yellow book which is sitting on top of the bookshelf to the left. Now, carry the book all the way back up the stairs – when you get to the top of the stairs, look straight ahead of you and you’ll see a line of yellow books with one missing. Put the book in this slot and the shelf will open up and drop out the Red Gem.
Gem #5 – Master Bedroom
Go into the Master Bedroom and use a Burst (ZR + ZL) to make all of the lasers show up. Now that you can see where you need to go to avoid them, make your way to the mannequin in the top right corner and perform a Suction Shot on its chest to flip the bed around, revealing a moving platform underneath. Now, summon Gooigi and move from left to right on the platform to make it swing either way, and the momentum of it will cause it to raise slowly. Do this until you reach the top of the room and you’ll see the Yellow Gem behind a set of bars which you can slip through with Gooigi.
Gem #6 – Master Bathroom
Go into the Master Bathroom and work your way around to the top right corner of the room. Use your vacuum on the massive tap to turn off the shower, then summon Gooigi and slip through the grate in the floor. Pretty much immediately as you drop down there’s a little tunnel that you can run down to your left which is slightly hidden because of the camera angle – run down here and go through the pipe and you’ll come out on the wooden beam above, allowing you to grab the Blue Gem.
And that’s it! Congratulations, you collected all six gems.