No.  At least, not like Emma.  They turned their hearts into diamond to trap the Phoenix Force in there.  That's all though. 
 
Grant Morrison's run is when Emma first turned into diamond & when the Cuckoos were first introduced.  By then, Emma was a grown woman after years of being a telepath.  The Cuckoos were less than a year old.  So there's nothing to suggest that they should have exactly the same abilities as Emma from the very start, when she had only just developed that ability.

Double Huh?? I'm about 99.999999999 percent sure they can't turn into diamond

" @kerukun878 said:

" @xerox-kitty: Actually, other then in Warsong, the Cuckoos have been seen to become Diamond. "

Right. The Stepford Cuckoos can turn into indestructible diamond form, unlike Emma Frost. "

Is it true that they can't feel no emotions because of their diamond hearts?

Unlike Emma their diamond form is flawless .

I'm sure they can feel emotions now since the shard of the phoenix left their hearts during the Nation X story arc hence them not needing diamond hearts anymore. And in recent post avx issues of Uncanny X-Men they (specifically Celeste) displays emotions like anger/animosity towards time displaced Jean Grey and also (again Celeste lol) freaking out on Irma(Mindee) for cutting and dying her hair black.

@kallarkz Most recently they've turned into diamond form in Uncanny X-Men Issue 6 (post AVX) when Magik unwillingly transports them into limbo to get ambushed by demons. They don't hold this form for long only because they decide to use their telepathy instead to amplify the new group of mutants' bravery. I guess this confirms they can't use their telepathy in diamond form like Emma Frost.

HA!

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