Gemstones are very well hidden items in Luigi's Mansion 2. There are five different types for each mansion;


Luigi collecting Gloomy Manor's third Gemstone in the Parlor

Amethysts are in the Gloomy Manor. Emeralds appear in the Haunted Towers. Rubies are in the Old Clockworks. Sapphires are in the Secret Mine, and diamonds are in the Treacherous Mansion. Each is hidden very well, and the player must have a keen eye to spot clues to where they are. For each mansion there are 13 different gemstones, each with a different shape. Collecting all the gems will unlock a special statue of Luigi for the player to admire. It is decorated with the gems that were collected.

The locations for each are recorded below:

Gloomy Manor

Shape Image Missions Available Room Obtaining
Circle Lmdmgems1 All Mudroom Exterior Use the Poltergust 5000 to take it down from the tree.
Triangle Lmdmgems2 All Front Yard Use the Strobulb to make the flower in the middle of the patch to the left of the staircase bloom. It will give the gem.
Rectangle Lmdmgems3 All but A-1 Parlor Use the Strobulb on the clock.
Football Lmdmgems4 All but A-1 Studio Looking through the camera will let the player see the gem through the mirror. Aim out the window and suck it up.
Tear Lmdmgems5 A-3 and Bonus Entrance Check the suit of armor on the right to make it's head fall off. Suck up the helmet and shoot it at the painting of a knight head. It will open up and make a gem appear.
Stone Lmdmgems6 A-3, A-4, A-5, and Bonus Dining Room Find the safe at the right side of the room on the ceiling and use the Strobulb on it.
Rhombus Lmdmgems7 A-3, A-4, A-5 and Bonus Kitchen Open the fridge to reveal the gem encased in ice. Then check the furnace to start a fire. Suck up the ice block and move it over to the fire, freeing the gem.
Star Lmdmgems8 A-3, A-4, A-5 and Bonus Foyer In the Patio, go left and use the Dark-Light Device on the wall, revealing a door to Under the Stairs. Go though the next door to end up on the other side of the fish tank, allowing access to collect the gem.
Octogon Lmdmgems9 A-3, A-4, A-5 and Bonus Patio Use the Dark-Light to reveal the third fountain that's next to the other two.
Oval Lmdmgems10 A-3, A-4, A-5 and Bonus Library Reveal the globe at the left side of the room. Suck it up and shoot it our for the gem.
Spindle Lmdmgems11 A-2, A-3, A-4, A-5 and Bonus Study Suck up the curtains on the back wall to uncover a painting of the gem. Use the Dark-Light to make it a reality.
Coffin Lmdmgems12 A-5, and Bonus Rafters Go to the lower-right corner of the room, with the dresser. The gem is in plain sight, resting atop the dresser.
Mushroom Lmdmgems13 A-5, and Bonus Bedroom Burn the webs with the spider web. Go behind the covers to obtain the final gem.

Haunted Towers

Shape Image Missions Available Room Obtaining
Circle Lmdmgemsht1 All Tower Lobby Walk behind the stairs to find and obtain the gem.
Triangle Lmdmgemsht2 B-1 and Bonus Laboratories Use the Balloon Berries to fly down into the glass chamber from the floor above.
Rectangle Lmdmgemsht3 B-2, B-3, B-4, B-5, and Bonus Garden Fill up a bucket with water, and water the flower on the right side of the Garden. It will reveal a gem.
Football Lmdmgemsht4 B-2, B-3, B-4, B-5, and Bonus Botany Lab Fill up the bucket in the room with water, and water the plant in the back of the room. It will reveal a gem
Tear Lmdmgemsht5 B-2, B-3, B-4, B-5, and Bonus Seedling Laboratory After clearing the room, use the potato shooter to shoot the mouse carrying the gem, then collect your reward.
Stone Lmdmgemsht6 B-3, B-4, B-5, and Bonus West Garden Reveal some pipes using the Dark-Light on the stairwell of the Tower Lobby, and then reveal a door on the left side of F1 in the Tower Lobby. Use the hitchhiker plant to kill the Carnivorous Plant. Open the chest.
Rhombus Lmdmgemsht7 B-3, and Bonus Hollow Tree Use the cobwebs to burn your way through the left tunnel. Take the bucket from the left and fill it with water. Then go right to water the plant. Use the Strobulb for your reward.
Star Lmdmgemsht8 B-3, B-4, B-5, and Bonus Old Cemetery Take it down from the tree branch it sits upon, just before the main part of the graveyard.
Octogon Lmdmgemsht9 B-4, and Bonus Skybridge Defeat the Orange Flowers to get the gem.
Oval Lmdmgemsht10 B-4, and Bonus Rumpus Room Walk around the doll counter-clockwise to pop its head off and find the gem.
Spindle Lmdmgemsht11 B-4, B-5, and Bonus Solarium The the Dark-Light to reveal a chest on the table. It contains the gem.
Coffin Lmdmgemsht12 B-4 Conservatory (Luigi's Mansion 2) Using a Balloon Berry to fly to a balcony to the right, use the Dark-Light to uncover a door. Go in the door and beat the challenge to earn a gem.
Mushroom Lmdmgemsht13 B-4, B-5, and Bonus West Bathroom Defeat all the ghosts and pull on the toilet paper to the left.

Old Clockworks

Shape Image Missions Available Room Obtaining
Circle Lmdmgemsoc1 All Clockworks Court

Go far right and use the Dark-Light on the tool box containing a gem.
Triangle Lmdmgemsoc2 All Warehouse Use the Dark-Light to reveal a green barrel on the boxes. Use the machine in the room to reveal the gem.
Rectangle Lmdmgemsoc3 All and Boss Clock Tower Gate In the top-left corner of the room, use the Dark-Light on a tool box containing a gem.
Football Lmdmgemsoc4 All but A-1 Storm Cellar Suck up the sheet in the bottom-left, and use the Dark-Light on the painting.
Tear Lmdmgemsoc5 All but A-1 Canyon Stairs There is a ruby stuck in a web that you'll see as you go up.
Stone Lmdmgemsoc6 All but A-1 Quarry Pull the mine cart so that Luigi can go into the tunnel behind it. This will lead to several Golden Bat (Luigi's Mansion 2), and the gem.
Rhombus Lmdmgemsoc7 C-3, C-4, C-5 and Bonus Clockmaker's Chambers Suck up the rug to find a gear. Use the gear to turn the clock to 9:00, which will wake up the ghost holding a ruby. Defeat it to get the gem.
Star Lmdmgemsoc8 C-3, C-4, C-5 and Bonus (Upper) Roundhouse Walk along the rightmost beam, on the balcony of the Roundhouse. walk around the corner to find a chest with a gem.
Octogon Lmdmgemsoc9 C-3, C-4, C-5 and Bonus (Lower) Roundhouse From the stairs leading to the (Upper) Roundhouse continue going left into a secret area with a gem.
Oval Lmdmgemsoc10 C-5 Gear Chamber Go across the boxes on the right side of the bottom part of the room, revealing a bridge along the way. Go into the hidden door and complete the challenge to get a gem.
Spindle Lmdmgemsoc11 C-5 and Bonus Maintenance Hub Use the hipline to fall into the bottom of the room. Reveal a chest in front of the giant gear. The gem is inside.
Coffin Lmdmgemsoc12 C-5 Service Elevator After getting Toad, launch him towards the screen. He'll collect some Secret Mines
Mushroom Lmdmgemsoc13 Boss and Bonus Movements Walk to the window on the left and vacuum for a gem.

Secret Mine

Shape Image Missions Available Room Obtaining
Circle Lmdmgemssm1 All Smokehouse Use the Dark-Light to reveal a scarf on the wall, then pull both of them off.
Triangle Lmdmgemssm2 All Fishing Hut It's hidden in the bottom-left. The player can see it from the hole outside the hut. Use the Poltergust 5000 there to get it.
Rectangle Lmdmgemssm3 D-1 Under the Ice Shoot Toad into the wooden shaft after riding the first air geyser.
Football Lmdmgemssm4 All High Wires Use the zip lines to cross the first chasm, and take the gem down from the bird's nest.
Tear Lmdmgemssm5 All Airway Look through the binoculars at the entrance to the Terminal. Look for the dark cave and you'll see a bat go from the cave and drop the gem into a barrel. Go collect it afterwards
Stone Lmdmgemssm6 All but D-1 Chalet Approach Outside to the left of the entrance is a stove, with a chicken on top. Light the stove and use the flaming chicken to melt the ice around a painting outside. Use the Dark-Light on the painting, and collect the gem.
Rhombus Lmdmgemssm7 All but D-1 Prospector's Crossing On the lower left wall is an axe that is hidden with Spirit Balls. Uncover it with the Dark-Light (there is a hidden arrow pointing to it in the ice). Use the Poltergust 5000 on it to find two logs. Put both on the ice to break it, and collect the gem that was inside.
Star Lmdmgemssm8 All but D-1 Skip Slope While sliding down be prepared to go to the left. There will be a big spinning wheel blocking a path to a gem. The player must slide through one of the holes in the wheel to get it. This may take a couple of tries.
Octogon Lmdmgemssm9 All but D-1 Shaft Pull the chain at the bottom of the Shaft, then climb back up to a hatch that was previously closed. The gem is inside.
Oval Lmdmgemssm10 All but D-1 Deep Hall Light a piece of coal, and look up. There should be a gem encased in ice above. Shoot the coal at the ice to melt it and ma,e the gem fall to the ground.
Spindle Lmdmgemssm11 D-3 and Bonus Crossroads Go to the left side and find the missing mine cart with the Dark-Light. Quickly go over to the right side to capture the Spirit Balls. Return to the left side to find the gem hidden in the snow.
Coffin Lmdmgemssm12 D-3, and Bonus Chalet Go to the very bottom of the mine, in the Crystal Quarry. In that room there should be a portal that can be activated with the Strobulb. Go though and you'll end up in the Chalet. Luigi will land on a chair, knocking the gem from it's hiding spot.
Mushroom Lmdmgemssm13 D-3 High Wires Use the coal shooter to melt the ice on the tree. Go cross the tree to an outhouse. Go inside and hit the three Hiders with snowballs to win a gem.

Treacherous Mansion

Shape Image Missions Available Room Obtaining
Circle Lmdmgemstm1 E-1 and Bonus Underground Lab After turning the wheel to maximum poser to zap the armor, use it's helmet to knock down the beakers. One of them has a gem.
Triangle Lmdmgemstm2 E-1 and Bonus Haunted Catacombs After the Underground Lab, follow the direction the suits of armor point shen checking them. At the last tunnel with no suits of armor, go to the farthest back point and go right. Use the Dark-Light on the painting of a spider web and light it with the fire nearby. Burn the webs you saw along the way for a gem.
Rectangle Lmdmgemstm3 E-1 and Bonus Cliffside From the Underground Lab door go right, down, right, and up twice. This will lead you to a door that goes to the Cliffside. Take the gem down from the vine.
Football Lmdmgemstm4 E-2, E-3, E-5, and Bonus Front Entrance Reveal the missing chain attached to the gargoyle statue. Pull it and open the safe under the stairs for a gem.
Tear Lmdmgemstm5</span> Restrooms Pull the chain on the toilet in the western side of the room.
Stone Lmdmgemstm6 E-2 and Bonus Gargoyle Roof Pull on the mammoth trunk in the Ice Age Exhibit to access the Gargoyle Roof. Find three stars around the "room" and shoot them into the giant star made of smaller stars. A gem will fall from the sky upon completion.
Rhombus Lmdmgemstm7 E-2, E-3, E-5, and Bonus Ancient Exhibit Water the spout close to the door, and use the Strobulb on the plant that appears. A gem will pop out. You can find the bucket in the Dark Age Exhibit and the water in the Jungle Exhibit. Use portals to traverse.
Star Lmdmgemstm8 E-3, E-5, and Bonus Aviation Exhibit Pull all of the sandbags off the hot air balloon.
Octogon Lmdmgemstm9 E-3, E-5, and Bonus Nautical Exhibit Place something like a log or a bucket of water of the life savior on the ship to make the wheel go down. Go out to the end of the ship and open the chest with a gem in it.
Oval Lmdmgemstm10 E-3, E-5, and Bonus Dark Age Exhibit Using a Balloon Berry, fly up and right to find a gargoyle with a blue book. Use the Strobulb on it to make it drop the book and fly back down. Put that book into the bookshelf in the Dark Age Exhibit.
Spindle Lmdmgemstm11 E-3 Jungle Exhibit Either use a Balloon Berry or enter from the East Balcony to get to the top part of the Jungle Exhibit. Find the Golden Balloon Berry and collect all the coins for ca chest with a gem in it.
Coffin Lmdmgemstm12 E-3 Ice Age Exhibit Use a Balloon Berry to fly to the tiop left portion of the Ice Age Exhibit. Collect all the coins from the Golden Balloon Berry for a chest with a gem in it.
Mushroom Lmdmgemstm13 E-3, E-5, and Bonus Train Exhibit Use the Dark-Light on the missing track in front of the door. Afterwards ride the train once for a gem.