Fluorite

This distinctly asymmetric pair of ex-matrix, interpenetrant twinned Fluorite crystals forms an excellent example from the Sherry Twins Pocket at Lady Annabella mine, close to Eastgate in County Durham. The two crystals measure 4.5 x 3.2 x 2.9 cm (diminishing from 2.9 to 1.0 cm at the opposite end) and 1.9 x 1.9 x 1.8 cm. The base of the large crystal becomes translucent milky-white on its base, across where it has been broken away from the original matrix. Both crystals are mainly transparent and contain large gemmy zones of light sherry-brown carrying a distinct glow of warm lilac. The crystals are colour zoned, especially along their faces and edges, in bands of pale cucumber-green punctuated with a pencil-thin line of lavender. Under LWUV the entire specimen fluoresces a bright lilac-white, although the crystal edges emit a brighter lavender-white framework which nicely delineates the overall morphology.

The Lady Annabella mine began specimen recovery operations in July 2020 within the former Eastgate Quarry, previously known as the Blue Circle Cement Quarry. This quarry began in the early 1960s, working an exposure of the Great Limestone, a major formation of Carboniferous age (Pendleian Substage), found across much of Northern England. Following uplift and fracturing, subsequent Fluorite mineralisation pervaded this area of County Durham, in the form of sub-vertical veins and near-horizontal metasomatic flats. Metasomatism is the chemical alteration of rock by hydrothermal fluids. Over the past 55 years, Fluorite from this quarry has become famous amongst collectors for its wide range of colours, colour variations and zonation. In just its first five months of operation, the Lady Annabella mine has produced a magnificent range of Fluorite specimens, many of which are colour variants and mixtures never before seen at this locality, nor even in the other famous mines throughout the Weardale Valley.