Corundum Visible Spectra (generally 350 - 1200 nm)
Corundum occurs in several colored varieties. Ruby is red because of its
Cr3+ content. Yellow sapphire owes its color to Fe3+.
Blue sapphire derives its color from the Fe2+ - Ti4+
and the Fe2+ - Fe3+ intervalance charge transfer.
Green sapphires contain a mixture of the blue and green colors.
Images of representative corundums
Ruby GRR 1843; Ruby obtained in Chathaburi, Thailand, 0.787 mm thick, looking down the
c-axis. All the features are from Cr3+ including the sharp spin-forbidden
band near 695 nm. Data files: a, 24K;
Ruby GRR 1843; Ruby obtained in Chathaburi, Thailand, 0.758 mm thick, looking down the
c-axis. Spectra as a function of temperature (27, 300 and 600 C). Data files: 27 degrees, 19K;, 300 degrees, 19K;, 600 degrees, 19K;
Ruby GRR 1843 animation; A movie showing the change of color of ruby 1843 as a function of temperature: 0.758 mm thick, looking down the c-axis (795 KB).
Sapphire GRR 1020 (6K); Medium
blue sapphire from an unknown locality (probably in Australia) presented
normalized to 3.00 mm thick. All the sharp features are from Fe3+
and the broad features which dominate the spectrum are from intervalence
charge transfer between Fe2+ and Ti4+ and between
Fe2+ and Fe3+. Data files: a,
15K; c, 26K
Sapphire GRR 1798 (6K); Pale
blue sapphire from the Missouri River near Helena, Montana, 3.23
mm thick, looking down the c-axis. All the sharp features are from Fe3+
and the weak, broad features are from intervalence charge transfer between
Fe2+, Fe3+ and Ti4+. Data files: a,
Picture of a zoned sapphire crystal
from Laos with clickable spectra in different
no other data files
Corundum Infrared Spectra (generally 4000 - 3000 cm-1)