Welcome to TNet Nancy! This an interesting acquisition but I can only give you the opinion of a mostly confused old man. First of all, the media seems to be some kind of concretious material. All the little rocks inclusive in the piece are the aggregate for some kind of composite probably held together with some form of lime compound. The piece looks to have been painted sometime probably in the 20th century. This piece, IMO, was probably cast in a mold maybe imprinted in native clay. Often as not native carvings depict historic events, natural phenomenon or human commemoratives (usually busts with elaborate dressings). This guy seems to be sitting in a fairly modern wooden chair.
I'm not a definitive expert and have known many antique dealers both honest and other. You might want to invest in items that come with some sort of provenance! Nice token for your front porch or accent piece for your patio. Best wishes!