Mega Stones

[Mr. Suplado]

What are the available mega stones? And where is their location?

[Starry Knight]

Spoiler

Abomasite Near Kingsbury need blizzard to navigate and water fall

Aggronite Grand hall basement talk to scientist in main room to start quest

Altarianite Glass Factory top floor

Blastioseite RT 4 on way to get Bagon need heat wave

Heracross/Pinsir Advertrine forest N talk to NYu with a Blue moon ice cream in bag cannot have any other candy in bag

Banettite Trade a Floral charm in  city

Sabeleye Glass factory main floor

Gallade, Mawile Bee's quest Argate CITY

Gardevoir/Magnetric Password quest

Amphorose Grandhall basement inerigation room

These are just ones off top of my head currently

[Vanitas]

Additonally:

absolite

aerodactylite

audidinite

beedrillite

cameruptite

charizardite x

glalite

houndoomite

kangashkanite

lopunnite

manectite

mawilite

medichamite

pidgeotite

pinsirite

sceptilite

sharpedonite

steelixite

venusaurite

most of them are quest rewards or rather easy to find if you explore (i forgot there locations at this point)

and i just saw a E 18 item guide somewhere so... good luck

[Starry Knight]

Abomasite: 
Ametrine Mountain B3F, start by reaching Ametrine F1 by climbing up the Waterfall in Celestine F1 (Celestine Cascade entrance) or jumping the ledge and climbing down the Waterfall in Ametrine F2 (Calcenon/Route 3 and Route 2 entrance), open the ice-Strength puzzle by pushing the boulder from one side of the Waterfall and going through the path from the other, go through the Dive spot and through the cave opening at the right (surf over it downwards), resurface to B1F and go to the left in the ice skating puzzle, go into the Dive spot and through the cave opening at the low left into B2F (the Lapras location), go through another cave opening at the bottom left to B3F and find it next to the X Door at the left

Audinite

Azurine cave - requiers surf,dive, waterfall and blizzard

 

Cameruptite

Crysolia spring sauna

 

Glalitite

Azrine lake dive, S9