A Trinket from Majuba Hill

Rhyolite from Majuba Hill, in the shape of Nevada (a pin).

As per this little blurb (above) by the NBMG, tourmaline (the black mineral) has replaced the sanidine and plagioclase feldspar phenocrysts, leaving small blobs and fairly large eyes of translucent and very light gray to faintly yellowish or tan quartz amongst the often large masses of tourmaline. The one tourmaline mass or crystal near the center of Nevada — right about where Kingston Canyon, south of Austin on old Highway 8A, would be — retains the shape of a feldspar, probably a K-feldspar (sanidine).

Surprisingly, not all rhyolite porphyry from Majuba Hill comes in the shape of Nevada.