Hello Lal,
thank you for your reply.
I still cannot reconcile that:
There must be a trace of matter for the mind to exist AND Nibbana is pure mind beyond matter (not exactly your words but cannot find the original source at this time but the idea stays the same).
Until now, to me, Pure consciousness is the source of everything including the mind, and pure consciousness is of course beyond matter either gross or subtle, even slightly condensed energy like gati or dhamma.