• Fluorite with Siderite

Fluorite with Siderite

ID: CC20921
This splendid interpenetrant twinned fluorite is from the Sherry Twins Pocket at Lady Annabella mine, near to the village of Eastgate in Weardale. The twins measure 3.0 x 2.9 x 2.2 cm and 2.8 x 2.5 x 1.7 cm and are off matrix with a rough cloudy base from where they were attached to the host rock when in-situ. Each crystal has mirror-smooth surfaces which display nested square and rectangular growth patterns and although glassy, do have a slight waxy lustre. Each crystal also has some faces which are convexly-curved, an unusual morphology for Fluorite. Their colour is the distinct shade of medium sherry-brown characteristic of this pocket, with hints of light caramel. The crystals also exhibit zoning with outer colourless shells grading through subtle purples and greens to the inner sherry and reasonably gemmy cores. To lend additional charm, one end of the larger crystal is coated in dark chocolate-brown etched crystals of Siderite. Under LWUV the crystal outer edges fluoresce lavender-white, forming an outlining framework while within this the faces are mid-lilac. The Siderite does not fluoresce.

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.

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4.0 × 5.2 × 3.5 cm
Fluorite and Halides, Latest Additions
Sherry Twins Pocket, Lady Annabella Mine, Eastgate, Weardale, County Durham, England, Europe

Minerals on Specimen

Minerals on specimen
Fluorite, Siderite

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