This is a specimen labelled descloizite, Grey Horse Mine, Riverside, Riverside Mining District, Dripping Spring Mountains, Pinal Co., Arizona, USA.
It is yet another addition to my Hidden Collection.
The specimen consists of a few dark brown descloizite crystals, which are quite nice in themselves, and then under the microscope, you can see a lot of calcite crystals.
But it is when you illuminate it with shortwave ultraviolet light that it gets really interesting! Note that there is no response under longwave or medium wave UV light.
First thing you notice is the “Mercedes” faces on some of the crystals, so-called because they look like the Mercedes emblem. This is a late addition to the calcite crystals and you can see ragged edges when you zoom in. The second thing that you notice is that the fluorescence is not consistent through the crystals. It is zoned in the centre of the crystals, with a subsequent non-fluorescent deposition, followed by the Mercedes faces.
Click on the images for a higher resolution version.
Below: Descloizite, Calcite, Grey Horse Mine, Riverside, Riverside Mining District, Dripping Spring Mountains, Pinal Co., Arizona, USA. Width of view 6mm. SWUV.
Below: Descloizite, Calcite, Grey Horse Mine, Riverside, Riverside Mining District, Dripping Spring Mountains, Pinal Co., Arizona, USA. Width of view 6mm. White light.
A world in a grain of sand…