Colors from metal ions in minerals

All of the examples of colored minerals on this page have color due to metal ions.  Ions of the first row transition elements (Ti to Cu) are normally responsible for color in these minerals.  These ions have electrons in the five 3d orbitals. In the crystallographic sites found in minerals, the 3d orbitals split into different energies. Visible light interacts with these electrons and causes them to be excited to higher energy orbitals. The wavelengths that cause these transitions are subtracted from the incident light resulting in color.

First Row Metals

Other Metal Ions

Mineral Spectrum Mineral Photo
bastnäsite bastnäsite
monazite monazite
titanite titanite

The rare-earth elements have distinctive colors in the 3+ oxidation state and distinctive absorption spectra that change little with different hosts. Here are some examples of synthetic rare-earth garnets and phosphates.

element compound photo   element compound photo
La - colorless        
Ce(3+) - colorless     Tb  
Pr Ga Garnet     Dy Ga Garnet  
Nd Ga Garnet     Ho Al Garnet  
Pm is not naturally occuring     Er  
Sm Ga Garnet     Tm  
Eu Ga Garnet     Yb  
Gd - colorless     Lu - colorless  

Several of the garnets illustrated show evidence of contamination by other rare-earths - better examples to come in the future

Often asked questions about color in minerals

Back to the list of causes of color

Back to the Mineral Spectroscopy home page

last updated: 30-Apr-2006