Minas de ópalo de La Trinidad

The hills around La Trinidad, a small community west of Tequisquiapan, hold some of Mexico's fire opal, a semi-precious stone of volcanic origin that glows in reds, oranges and yellows. Querétaro has long been the heart of opal mining in Mexico, and for more than a century the stones from this area have been cut and polished in Tequisquiapan and sold as jewelry around the world.

The mines are privately owned, but several of them welcome visitors on guided tours. You ride out in a 4x4 along dirt tracks, walk into the reddish mine workings, and learn how the opal forms and how it is extracted. Then you get a hammer and chisel and try your luck: whatever you find, you usually keep.

Many tours end at a workshop where you can watch the stones being cut and polished, and buy finished pieces. It is a half-day outing that works well for families and makes a change from wineries and hot springs.