More Minerals

I celebrated my 48th birthday a little over a week ago. I got a package from Jeff Shallit, whose avocation is minerals. Diane and I have met up before with Jeff and his family in the desert southwest, a destination he enjoys particularly for the opportunity to apply geological knowledge and find minerals for himself. Last fall, I accompanied Jeff to a mineral and gem show in Detroit. I had expressed some interest in a couple of types of minerals, and Jeff kindly sent along a couple of samples.

First up is a piece of pyrite, FeS2. This one comes from Navajun, La Rioja Province, Spain. It is a cube, 19.03×19.20×19.31 mm in size. (Electronic readout calipers are cool.) The surfaces are almost mirror-like, and it is somewhat challenging to show any surface texture on the pyrite at all.

And the second is a sample of fluorite, this one from the Rogerley Mine, Frosterley, County Durham, England.

But the real attraction of fluorite isn’t evident until you hit it with ultraviolet light. I took apart a UV light keychain LED bob and a cheap Garrity LED flashlight, and replaced the Garrity white LED with the UV LED from the keychain bob. (Actually, I’ve brought the leads out to a two-place screw-in terminal. I can swap out LEDs for the light of choice.) This gives me a handy UV source I can use in close-ups.

The photo setup is based on a copy stand I made from an old, cheap enlarger. I got rid of the head and simply use the attachment point to mount my camera. The background is a sheet of coarse-grit sandpaper glued down on mounting board. I tilted the whole thing to take the pyrite shot, since with everything flat one sees only two faces on the cube from directly above. The camera is a Nikon D2Xs, and the lens is my old Micro-Nikkor 105mm f/2.8 AIS manual-focus lens. I was shooting at 100 ISO, and given the mixed lighting, the exposure was several seconds at a small f-stop.