The spinels are a diverse group of minerals with wide
variation in their chemical composition. Among the more common
spinel group minerals, the color is due to chromium and iron.
Rarely, cobalt will be a cause of color.
Visible Spectra (generally 350 - 2500 nm)
Natural Spinels
- Red Cr-spinel,
Sri Lanka. The color comes from Cr3+. data file
- Blue
cobaltian spinel, Yakutia kimberlite pipe, Russia.
Approximately 0.05 mm thick. The color comes from Co2+ in the tetrahedral
site. Contributed data from Michail N. Taran, Kiev:
data file. Picture of the crystal
and the area of measurement.
- Blue
cobaltian spinel, Samos Island, Greece.
Plotted normalized to 10.0 mm thickness. The color comes from Co2+ in the tetrahedral
site. Contributed data from Michail N. Taran, Kiev:
data file.
- Blue cobaltian spinel,
Baffin Island, Nanavut, Canada. The blue color of the crystals comes
from Co2+ in the tetrahedral site. 0.849 mm
thick. data file
- Blue gahnite,
locality unknown. The color is from Fe2+. data file
- RDS-153c
Pink spinel from Tanzania containing both Cr3+
and Fe2+. Here we see the near-infrared region
showing the absorption bands from Fe2+ in the
tetrahedral site. 0.503 mm thick; 1.028% FeO. Sample Sp3
of Shannon & Rossman (1991) J Phys Chem Solids 52,
1055. data file
Synthetic Spinel-group materials
- MgAl2O4:Cr
spinel, synthesized by the flux method in
Novosibirsk, Russia. Normalized to 10.0 cm.
Colored by Cr3+. Data File: Contributed
data from Anton Vasiliev, LAL, Moscow: Spinel_Red, 25 K.
- MgAl2O4:Co
spinel, synthesized by the flux method in
Novosibirsk, Russia. Normalized to 10.0 cm.
Colored by Co2+. Data File: Contributed
data from Anton Vasiliev, LAL, Moscow: Spinel_blue, 25 K.
- Ni2SiO4
Spinel, published in Rossano et al. European Journal
of Mineralogy 1996:8, 471-475. Data file: Contributed
data from Stephanie Rossano, Paris: data file, 15 K.
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