American jade is made up of a group of semiprecious hard stones. Chief among them is a dense rock composed almost entirely of the mineral jadeite, a sodium aluminum silicate of the pyroxene family noted for its beautiful color when worked. The rock is extremely durable and very rare, and it was used in two ancient American regions: in Mesoamerica, where it is believed to have been made initially into simple items such as beads around 1500 B.C., and in the part of Central America now known as Costa Rica, where the first sculptural forms were probably carved about a thousand years later. As in China, where semiprecious hard stones—also known collectively today as jade—were worked from very early times, the initial use of such stones is thought to be an outgrowth of the production of tools, weapons, and ornaments of more common stone. Its compact structure, hardness, and admirable surface gleam when polished recommended jade for works of special status. Salient among those objects in the Americas was the celt, or ax, which was a working tool. The form of that tool then took on a symbolic aura of its own and it was used for objects of all sorts, from pendants to ritual objects.
Many American works of art in jade are green in color with widely varied tonal values—ranging from a pale apple hue, to a distinctive blue green, to almost black—where the basic “greenness” remains significant. In ancient Mesoamerican thought, green was the color associated with rain, water, and young growing plants, all highly meaningful to the societies dependent upon them for survival.