I spent much of the weekend reading up on, of all things, manganese chemistry. It turns out that there is a tourist mine in Salida, Colorado, that offers a glimpse of a manganese mine. It is rather dramatically called the Lost Mine and the tour includes a 4WD ride to the site. This tour is on the master list of future visits – my teenage kid groaned when I let this news slip out. Pretty funny.

What piqued my interest is a rock I picked up at a rockshop in Leadville recently. It is a low grade sample of dispersed rhodochrosite with a bit of pyrite grown into it. Rhodochrosite is a light pink to rose colored semi-precious crystalline mineral and also happens to be the state mineral of Colorado. It is fairly scarce and increasingly sought after for collection and for jewelry.

The light pinkish color of rhodochrosite stems from the oxidation state of Mn- Rhodochrosite is MnCO3. Depending on the ligand, the Mn (II) will have a high spin d5 electron configuration. The high spin d5 configuration requires a forbidden electron transition consisting of a jump between d orbitals and a spin flip on absorption of hv. Since this is a low probablility occurance, the molar extinction is low and accordingly, the color of the xtal is faint.

A fellow at the CC&V mine lamented that the ore body they process for heap extraction is loaded with manganese. He said that once they move the rock from the pit, the Mn levels cause it to become a pollutant (or some other term) as defined by the EPA. Manganese seems to be relatively abundant in parts of the Rockies.

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