What is Kirksite?

All:

Well, now I know what Kirksite is (laughing at self with bright red
face). I guess all words that end in “ite” aren’t necessarily gems
or minerals. That’s one of the perils of having narrowly-focused
interests, although I also do a lot of metalsmithing and had never
heard of the stuff. That’s why Orchid is so great – always
something new to learn. And since I’m on the Digest version I always
learn things a day later than most of the rest of you.

Rick Martin