Fluorite

specimen number:
1052660

location:
Weardale, Co. Durham, England, UK

description:
Fine 19th-century example consisting of a large matrix plate covered with glassy fluorite crystals. Some damage present as seen. The largest crystals measure to 4.0 cm on edge. Incredibly fluorescent. The specimen comes with an antique label as shown at the end of the video. Previously from the collection of Wilhelm Hoyer. Both the photo and the video are taken in natural daylight.

The Weardale district, located within the North Pennines Orefield in County Durham, England, is world-famous for producing exceptional fluorite specimens, particularly those exhibiting deep emerald-green color and strong daylight fluorescence. Geologically, these deposits are hosted in Carboniferous limestones and sandstones, where hydrothermal fluids circulating through the Alston Block precipitated fluorite, galena, and quartz within nearly vertical fissure veins known locally as rakes. These veins often feature open cavities or pockets where fluorite crystals developed into sharp, interpenetrant twins of remarkable clarity and color. Historically, mining and underground quarrying in Weardale date back to the Roman period for lead, but the extraction of fluorite became a primary industrial focus in the late 19th and 20th centuries for use as a flux in steelmaking. Major operations at mines like Rogerley, Heights, and Blackdene reached their peak production between the 1880s and the 1980s, with most commercial industrial mines closing by the early 1990s. Through 2026, Weardale remains a premier global locality, with specialized specimen-mining projects at the Rogerley and Diana Maria mines continuing to provide the international market with the finest examples of English green fluorite.

Wilhelm Hoyer (1849-1913) was a prominent German engineer and mineral collector based in Hanover, whose professional work in railway construction and geology facilitated the assembly of a significant mineralogical collection. Geologically, Hoyer was noted for his deep expertise in the Mesozoic formations of northwestern Germany, particularly the Hildesheim area, where he meticulously documented and collected specimens from active quarries and construction sites. His collection was scientifically important for its comprehensive representation of regional minerals and fossils, reflecting the systematic approach of 19th-century European collectors who bridged the gap between industrial mining and academic mineralogy. Historically, Hoyer was active in the latter half of the 1800s and early 1900s, contributing numerous papers to geological societies and maintaining professional ties with major institutions of his era. Following his death, his extensive mineralogical and paleontological holdings were integrated into the collections of the University of Gottingen and the Prussian Geological Survey in Berlin, where they continue to serve as vital reference materials for researchers through 2026.

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