Some jahnsites

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JW
Posts: 249
Joined: Wed Feb 23, 2011 7:38 am
Location: New Haven, CT, USA

Some jahnsites

Post by JW »

The Jahnsite mineral group is a complex series of calcium-manganese-magnesium phosphates in which sodium and iron, amongst other transition metals, can be substituted in the Ca, Mn and Mg atom positions. These crystals are a mixture of Ca, Mn, Mg and Na, Fe, Mg dominant compositions, found on the same 3cm sample. Variations in crystal chemistry are responsible for the different colors, with the yellowish-green and orange being jahnsite-(CaMnMg) and the honey yellow being jahnsite-(NaFeMg). The white is carbonate-apatite and the dark brown is leucophosphate. Made with Mitutoyo 20X, WeMacro rail, reversed Raynox 150, Canon 50D, 2 micron steps, ZS Dmap with some Pmax touchup, a bit of PS for cropping and contrast only. I used an in-camera custom color balance with grey card to fix the warm shift of the lens. Horizontal field of view is 0.84, 0.93, and 0.70mm top to bottom. Specimen is from the Tip Top Mine in the Black Hills of South Dakota, USA
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It's not what you look at that matters, it's what you see - Henry David Thoreau

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