Putnisite Structure

Steven Dutch, Natural and Applied Sciences, University of Wisconsin - Green Bay
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No, not the love child of Vladimir Putin and Katniss Everdeen. It's a recently discovered mineral, so far rare, that is unusual for not being affiliated with any previously known chemical family of minerals. Its formula is SrCa4Cr3+8(CO3)8SO4(OH)16*25H2O, or pretty much what you'd get by dumping the contents of a chemistry set into a blender. The mineral was actually named for German mineralogists Andrew and Christine Putnis. I'd be thrilled to have something this unique and downright weird named for me.

This mineral is not here because it's abundant, quite the contrary, but because it's seemingly unrelated to anything else. Plus it has a very nifty structure. Viewed down the a-axis with the b-axis to the right.

putnisite structure

Where to begin? Considering its complex formula, the structure is pleasingly regular and easy to picture. Putnisite's structure includes:

The symmetry is orthorhombic and pseudo-tetragonal.

Putnisite Structure

Above: edge-on view. Atoms farther from the plane of the diagram are lighter. The light blue Ca units and the darker purple ones in the foreground are not linked. Viewed down c-axis, with b-axis to the right.

Putnisite Structure

Above: edge-on view. Atoms farther from the plane of the diagram are lighter. Viewed down b-axis, with c-axis to the right. The slanting lines are carbonate groups viewed edge-on.

Showing Hydroxyl and Water Molecules

Putnisite Structure

Above: viewed down a-axis, with b-axis to the right. Oxygen atoms are blue, hydrogen atoms are red.

Putnisite Structure

Above: viewed down c-axis, with b-axis to the right. 

Putnisite Structure

Viewed down b-axis, with c-axis to the right. The slanting lines are carbonate groups viewed edge-on.


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Created 08 March, 2016, Last Update 13 March 2016

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