In Joss Whedon's Astonishing X-Men run (issue 13, to be precise), there's a flashback to Cassandra Nova meeting Emma at the Master Mold in Ecuador and Nova tells her that she'll survive the Genoshan massacre due to a secondary mutation that she (Nova) will give to her.
Has this ever been refuted or this the actual canon origin of Emma's diamond form? Or was it just a scenario that Emma came up with in her own head to help her deal with her survivor's guilt?