The Stone Calendar Project has been studying rock art sites throughout the southwest and northern Mexico identifying glyphs that mark specific times of the year using unique light and shadow interactions. Many of the rock art sites exhibit evidence of additional cultural rituals that occurred at or near the calendar sites. One of the interesting findings is the presence of "ringing rocks", sometimes referred to as gong rocks in other parts of the world. These rare basaltic rocks have a unique microstructure that generates a ringing acoustic sound when struck. Ethnographic reports from the southwest reveal use of these rocks but with little additional technical information. Most of the ringing rocks identified have been elevated and supported at a few points, which provides free edges that are less damped, producing a clear bell like ringing tone. The locations at which the rocks are struck are easily identified and still produce a wide range of tones. The ringing rocks are generally located at rock art sites, occasionally with some glyphs and cupules engraved onto the ringing rocks.
Ringing or gong rock sites are well known and documented in Africa, India, parts of IndoChina, and a few locations in the southwest. Several sites have been located and studied in New Mexico and Arizona, consisting primarily of basalt composition, with a few of granitic origin. Even at the locations where ringing rocks are found, only a small fraction of the rocks exhibit these ringing acoustic properties