Question

What are the locations of all fossils in Pokemon X/Y?

Answer 1

Glittering Cave. Some fossils, however, must be obtained by using Rock Smash in the last room of the cave.

Source: Experience and here.

Comments

I think he meant other gen fossils, such as the old amber.

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The Old Amber is found there too. You just have to have a Pokemon with Rock Smash to get them.

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Every fossil in the game is found in Glittering Cave.