Fibrolite is related to such minerals as sillimanite, kyanite, and muscovite.  It is composed of highly metamorphosed shale, which started out as clays with quartz, calcite, feldspar, and other components.

Fibrolite axes are made from a type of fibrolite found only in an area near Truchas Peaks.  Not only is the stone itself distinctive, but the form into which it has been ground is also instantly recognizable.  Most noticeable is the sharp blade and the spiral groove where the handle is attached.

 

Because the fibrolite is found only in one place, axes made from it provide information about early trade networks.  Starting in the area around the Truchas Peaks, fibrolite axes were apparently traded to such widespread locations as Frijoles Canyon in Bandelier, San Lazaro Pueblo in the Galisteo Basin, San Ildefonso and other pueblos along the Rio Grande, and the Hopi villages in Arizona.