Recently, I was on a road trip to the provinces of San Juan and La Rioja. The main point of the trip was to see Parque Ischigualasto, Parque Talampaya, and guanacos.

But, there was an opportunity to take in one of my favorite type of little museums: a personal collection that got wildly out of hand. This is the Museo Piedras del Mundo:
The enterprising proprietor of the museum has put together three rooms of displays, which he will lead you through (Spanish only). The main gallery boasts a hell of a rock collection.
Pains are taken to give information on the chemistry of various minerals, which are indeed from around the world. There are also sections dedicated to the local geology.

A second room houses local archaeological finds (the region is rich in fossils and ancient human-made relics, as well as impressive rocks)…
…and also some truly alarming local creepy crawlies.

The third room houses the seashell, fish specimen, and photography collection (all the photos were taken by the museum owner).
You will easily burn more time in the museum than you thought you would. And it’s a fun little place! It is maybe just past the middle of nowhere, if you’re coming from San Agustín, closer to a very, very small village called Usno. There’s literally nothing around the place. It is, if I recall correctly, $100 pesos for entry, and it’s open from 8am to 7pm daily. He’s also got a little gift shop.