Rockhound State Park - Deming, NM - Rock-Hounding on Waymarking.com

From the park brochure:
"Located on the rugged west slope of the Little Florida Mountains, Rockhound State Park is a favorite for “rockhounds” because of the abundant agates and quartz crystals found there. Hiking trails provide spectacular views of the surrounding landscape.
Scattered throughout the park are rock and mineral specimens of volcanic origin. These treasures range from varieties of jasper, silica minerals, quartz crystals, chalcedony, Agate, and common opal. Visitors are allowed to take up to 15 pounds of the rock for their personal collections."

Geologically, the Little Florida Mountains are almost solely late Tertiary volcanic rocks. They include interbedded andesite, dacite, ash-flow tuff, rhyolite and fanglomerate intruded by rhyolite domes and dikes. These volcanic units are between 22 and 38 million years old and appear to extend less than 600 feet deep into the subsurface. Gray perlite, thunder eggs, jasper, onyx, geodes, agate, rhyolite and quartz crystals are among the more common minerals and rocks found in the park.

Despite the the name of the park, it is not particularly easy to acquire good mineral specimens. The primary mineral is jasper which is usually found as small outcrops in solid rock. Colors are red, white, pink and an attractive whitish banded agate form. Geodes, and thunder eggs occur in bands of softer rock, but the most obvious veins have been heavily excavated. The easily to found mineral is perlite, a shiny black glassy rock that is exposed at various locations in prominent deposits several feet thick. Collectors will need a large hammer, several chisels and a spade, along with a good bit of time spent on the hillside to acquire worthwhile specimens.

To assist the collector, the visitor center docents will provide information, plus there is a display of the minerals to provide a visual reference. The park gates are open daily, 7:30 AM to sunset. For the more serious minded, there is a campground with water and electric hookups in the park near the main collecting areas.