![3.0 Sillimanite-biotite granite. Allenspark, Colorado. Gray quartz, pink alkali (K-rich) feldspar, white plagioclase feldspar, and black biotite. Sillimanite forms tiny (invisible) needles near and within biotite grains. [The part of the hat rim showing in the upper left, providing scale, is 8 cm long.]](../3.0.JPG)
3.0 Sillimanite-biotite granite. Allenspark, Colorado. Gray quartz, pink alkali (K-rich) feldspar, white plagioclase feldspar, and black biotite. Sillimanite forms tiny (invisible) needles near and within biotite grains. [The part of the hat rim showing in the upper left, providing scale, is 8 cm long.]