Oaxaca is well known for it's black clay pottery - the only places it's found are in Oaxaca State in Mexico and in New Mexico in the States. I got to visit a couple of different workshops where it's made. The pottery is all hand-built without a wheel.
When the clay is leather hard, it's possible to cut patterns into it. The clay is also polished while it's leather hard, usually with a piece of crystal, and pit fired. If it's fired a long time, the clay can hold water, but it ends up a kind of gray. If it's fired for a shorter time, the clay turns out shiny and black, but is less practical. In the fifties, when plastic came on the scene, it was a lot cheaper than the pottery. But . . . the shiny black pottery was very pretty . . . and it was a big hit with tourists like me!
Here's the pieces I bought . . .