Nightstone

I don't know how things really stand, but for me, these gems have had a really low drop rate out of prospecting. They seem to be rarest even though in theory they share the same chances of dropping as other uncommon gems. Any feedback?

As far as Jewelcrafters are concerned, these are the new Chalcedonies of Cataclysm. Compared to other uncommon quality gems, these are usually quite hard to come by through prospecting, and they're needed for a good amount of purposes:

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• When skilling as a JC, the Nightstone Choker is probably THE most useful design across the board. Save them for this!
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• Once you've reached 475 skill, you will unlock the daily quests, and one of these is A Present for Lila. Fortunately, Blizzard decided to remove Gem Perfection from all specific daily cuts (which didn't register as valid cuts for the JC dailies on early Cata launch), making it a little less troublesome.
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• And of course, just like any other green quality gem, they're required to transmute Shadowspirit Diamonds if you want to level your JC quickly, once you can afford a design of your choice from tokens. There's no alternative to this at the near end of skilling up, except the Fire Prism design, which is on a 20h CD.
  
  Hope this helps. Enjoy!

i think he means it as though they are in the same demand as chalcedonay were. those things weren't exactly cheap as i recall, and neither are nightstone.