The following is a list of all 49 Mega Stones in Pokémon Unbound, and details on how to obtain them. If you click any image in the table you can see a full-size version.

You can also click any individual Mega Stone name to visit that stone’s wiki page with a step-by-step tutorial on how to obtain it.

Note: You’ll need to beat Successor Maxima in Tarmigan Mansion to gain the ability to Mega Evolve your Pokémon.

Mega Stone Location Screenshot
Abomasite Frozen Forest
Above the Crabominable’s Lair
Absolite Crystal Peak
Defeat Route Master Krystal
Aerodactite Crystal Peak
Inside No-Crystal Chamber
Aggronite Lost Tunnel
Behind a Rock Smash Rock
Alakazite Route 11
Defeat Route Master Timothy
Altarianite Tarmigan Mansion
Defeat Successor Maxima and gain Mega Evolution power
Ampharosite Thundercap Mountain 2F
Defeat Route Master Aloysius
Audinite Seaport City West Warehouse
Hidden Item – southeast corner
Banettite Grim Woods
Solve the Tablet Puzzle for Mission #007: Am I Blind
Beedrillite Grim Woods
Complete Mission #082: Weed Whacker
Blazikenite Cube Corp.
Mega Stone Maker, for 5 Fire Gems
Blastoisite Magnolia Cafe
(Post-Game)
Obtain from Cathy
Monday, 2PM-4:59PM
Cameruptite Cinder Volcano 3F West
MDefeat Mega Trainer Yale (requires Strength)
Charizite X Cinder Volcano 2F West
Solve the Tablet Puzzle for Mission #007: Am I Blind
Charizardite Y Magnolia Cafe
(Post-Game)
Obtain from Abimbola
Tuesday, 5PM-7:59PM
Diancite Grim Woods
Complete Mission #038: Major Miner
Galladite Antisis Port
Hidden Item, southeast crates accessed around 12pm
Garchompite Shadow Base 1F
(if Gible is starter) Found with the Level 2 Keycard in the west area where you found the starter

Mission Reward
(if not starter) Complete Mission #050: Portal Purge
Gardevoirite Vivill Warehouse
Inside a small chamber accessed via warp panel from B2F Power Grid
Gengarite Victory Road 3F Snowy Ascent
West of the Museum, up a Rock Climb wall
Glalitite Icicle Cave 1F
Defeat Skiers Club President Lily
Gyaradosite Route 13
Defeat Ocean Master Osean
Heracronite Mission Reward
Complete Mission #060: The Battle of Antisis
Houndoomite Shadow Base 3F
Defeat Zeph in his office during the main storyline
Kangaskhanite Redwood Forest
Defeat Mega Trainer Ravonna in a Kangaskhan Battle (must have 4 Kangaskhan in party)
Latiasite
or
Latiosite
Mission Reward
Complete Mission #042: No Survivors
(stone depends on your gender)
Lopunnite Route 2
Defeat Route Masters Vivian and Mathis
Lucarionite Mission Reward
Complete Mission #081: Warmonger
Manectite Thundercap Mountain 3F Tablet Chamber
Solve the Electric Gate Puzzle
Mawilite Icicle Cave 4F
Solve the Tablet Puzzle for Mission #007: Am I Blind
Medichamite Route 10
Defeat Mega Trainer Ernesto
Metagrossite Shadow Base 1F
(if Beldum is starter) Found with the Level 2 Keycard in the west area where you found the starter

Mission Reward
(if not starter) Complete Mission #050: Portal Purge
Mewtwonite X Post-Game Mystery Gift Code
6ZT5ZX7RN4KK
(held by the Mewtwo)
Mewtwonite Y Route 10
4QP1SH1BN8JF
(held by the Poipole)
Pidgeotite Route 17
Defeat Sky Master Almuth
Pinsirite Mission Reward
Complete Mission #044: Numbskull
Sablenite Route 18
Defeat Route Master Renna
Salamencite Victory Road
In 2F, on the other side of the Dive passage
Sceptilite Cube Corp.
Mega Stone Maker, for 5 Grass Gems
Scizorite Great Desert
Defeat Route Master Travon
Sharpedonite Mission Reward
Complete Mission #054: Shark Bait
Slowbronite Seaport City
South, on the small beach
Steelixite Fallshore City
Northeast area of the city, past a pond
Swampertite Cube Corp.
Mega Stone Maker, for 5 Water Gems
Tyranitarite Shadow Base 1F
(if Larvitar is starter) Found with the Level 2 Keycard in the west area where you found the starter

Mission Reward
(if not starter) Complete Mission #050: Portal Purge
Venusaurite Magnolia Cafe
(Post-Game)
Obtain from Mahina
Thursday, 2PM-4:59PM
Blue Orb Battleground
(Post-Game)
Defeat Vega on Monday, Wednesday, or Friday;
then, talk to Vega in Crater Town Gym
Red Orb Battleground
(Post-Game)
Defeat Vega on Monday, Wednesday, or Friday;
then, talk to Vega in Crater Town Gym