Board Thread:Questions and Answers/@comment-27509018-20170613025820/@comment-32360249-20170622130107

No, Elemental Mimicry converts organs, tissue, & blood (occassionally) into Rock/Metal-like substances, meaning the said organ will still have its fuctionality & perform as it should but possibly with more durability. An example is Collosus, in his Steel-Form his organs, flesh, & blood become Energy, possibly because if his skin is ever penetrated the organs would take no immediate harm but his mind is still active and he is not Psychic/Psionic Resistant. The Stepford Cuckoos would be more of an example for your question. They weild Selective Diamond Transformation & will convert their hearts to block emotion or potential damage to them, even their Brains thus preventing Telepathic Intrusion (but the still "have a brain").

But to sum it all up, depending on the senario, normally Elemental Substance Mimicry does not make one exactly immune to Telepathy, the mind is still active, and therefore can be invaded. A Rock Brain fuctions the same as a Real Brain, just made of Rock.