The Inner Beauty of Gems

Emerald, Be3Al2(SiO3)6 
green = Be, blue = Al, white = O, Si not visible here
Am. Mineral. 71, 977 (1986)

Ruby, Al2O3 
red = Al, white = O
Acta Cryst. A46, 271 (1990)

Quartz, SiO2 
pupple = Si, white = O
Am. Mineral. 65, 920 (1980)

Diamond, C
J. Appl. Crystallogr. 8, 457 (1975)