Crystal structure of high sanidine, a K-feldspar mineral.
Light blue: Si, Al (randomly distributed), purple: K, red: O.
The crystal structure was produced in the freeware [Vesta](http://jp-minerals.org/vesta/en/), using crystallograpic data from Scambos et al. (1987), downloaded from the [American Mineralogist Crystal Structure Database](http://rruff.geo.arizona.edu/AMS/amcsd.php).