Can Mewtwo's Mega Stone be obtained by defeating it instead of catching it?

[TokoyamiTheDark]

Exactly what the title says. A friend of mine is asking that question to be sure on how the Mewtwonite X/Y can be obtained, since he plans on using Pokemon Bank to get his own Mewtwo rather than catching it in the Unknown Dungeon... So, can the Mega Stone still be obtained even if Mewtwo is defeated rather than caught? :confused:

[Michael J. Caboose]

No.