OTHER EXAMPLES OF DETAILED EFFECTS

This information not required for students of EPS 2

CHANGING LOCAL ENVIRONMENT OF CATIONS

same impurity, different neighboring atoms:

Co++ in a tetrahedral (4-coordinated) site:

• in sphalerite (ZnS) causes green color
• in spinel (MgAl2O4) causes a blue color

same impurity, same valence state, different coordination environment

• Fe++ in peridot (6 coordination) - green
• Fe++ in garnet (8 coordination) - red

• Co++ in cobaltocalcite octahedral coordination - pink
• Co++ in spinel tetrahedral coordination - blue

• Mn++ in rhodochrosite (octahedral) - pink
• Mn++ in willemite (tetrahedral) - yellow