NEM is not a proof-of-stake coin, it is proof-of-importance.

And what about Blackcoin ?

As far as I understand, NEM is a Proof-of-Stake with a few modifications that developers call Proof-of-Importance, directed at artificially increasing velocity of money. Although these modifications need time to prove their efficiency, let's just call it PoS now to avoid confusion. You got to have something first, a stake, to participate in harvesting the blocks, right? So it's still a stake, not Proof of work.

I haven't tried Blackcoin. I meant pure 100% PoS cryptos with original source code. Isn't Blackcoin PoW/PoS based on Bitcoin code?