I suppose it would be more accurate to say I know someone who knows a thing or two about draenethyst. You see, the warlocks of the Burning Blade have been studying it. It is a substance from beyond the dark portal, so it follows that those involved with darker arts might wish to harness it to their own ends. We cannot allow this, obviously. The specific warlock you seek is named Gimashi. She can be found atop her tower, which is in a ravine to the southeast. Her notes will have the answers you seek.