The chamber contains giant selenite crystals (gypsum, CaSO4 · 2 H2O), some of the largest natural crystals ever found on Earth. It’s a unique place — let’s have a look at how these colossal ...

See photos of some of the world's largest crystals in a giant Mexico cave under Naica mountain—discovered by miners. By Stefan Lovgren and Ted Chamberlain. April 9, 2007 ...