Fluorite with Calcite

Bright, leafy-emerald green Fluorite crystals emerge from a snow-white coating of drusy Calcite which envelopes all save for the larger sized Fluorite crystals.  The Fluorite has not been etched out from Calcite by artificial means, the process is entirely natural in this part of the Diana Maria mine, west of the village of Frosterley in Weardale, County Durham.  This fine miniature is from the November Gem Pocket.  The 2.1 cm long interpenetrant twin is gemmy and shows delicate internal zoning, made subtle due to the slight variations in several shades of green.  The prisms display a surface layer of natural purple daylight fluorescence and under LWUV the entire specimen is a mottled patchwork of bright lilac white Fluorite scattered amongst non-fluorescent Calcite.