Not sure about the indigo, but it was definately the pure powder stuff.

Happy henna-ing!

It's for hair. And yes, I did end up tracking down both the red and black at a middle eastern grocer.

What is commonly referred to as black henna in a middle easter grocer is actually Indigofera Tinctoria or Indigo powder. It is a dark green powder and smells like frozen peas. If it is a black powder it is (as Amulya says) a synthetic dye and can be dangerous.
You can read about these technicalities at www.hennaforhair.com but once you know the real indigo you won't make a mistake. It's quite distinctive.

I have excellent results using red henna first then indigo afterwards to achieve an almost-black colour with just a hint of warmth to it.