I got mine from a dear friend. Its real volcanic stone from Bali and she picked it up on a trip there a few years ago. What good is a metate? Damn...tons of stuff.
My primary use is hand grinding small amounts of spices. Spices = seeds and barks as opposed to herbs...that are green leafy matter that is either fresh or dried.
Spices do best warmed until just toasty and aromatic in a heavy skillet then crushed to release all their oils and tossed into whatever you are cooking or roasting.
I use it at least once a day. The nice thing is as they get older they develop a patina and fragrance all their own. Nice way to freshen up the cabinet it resides in.
Funny how the most primitive tool I own is still my most useful.