Fluorite

This terrific miniature of well crystallised yellow Fluorite is from The Bull Vein at Lady Annabella mine, close to Eastgate in Weardale. A beautiful 1.0 to 1.2 cm interpenetrant twin, dusted with patches of micro-crystallised Quartz, stands near the centre of curved bed of single, colourless to pale lemon Fluorite cubes. Once again, this specimen exemplifies the observation that twinned crystals are often much larger than their corresponding single companions. The surrounding Fluorites are semi-transparent, with internal clouding and crazed with reflective flaws. However, the twin is perfectly transparent and gemmy, and has the unusual property that it can appear either colourless ice-clear, acidic lemon yellow, or a combination of both, depending on how it is held or displayed. In LWUV the Fluorite exhibits mottled purple, lilac and lavender fluorescence.

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.