Fluorite

specimen number:
9505686

location:
La Viesca mine, Huergo, Siero, Asturias, Spain

description:

Spectacular glassy blue gem cubic crystals of fluorite measuring to almost 5.0 cm on edge across the top of this sparkling quartz crystal matrix. This is in outstanding condition, especially considering the size of the piece. What at first appears to be cleaving on one corner is natural. Minor chalcopyrite present as well.

The La Viesca mine, located near Huergo within the La Collada mining district of Siero, Asturias, Spain, is a world-class mineral locality celebrated for producing some of Europe's most exceptional and highly aesthetic sky-blue and violet fluorite specimens. Geologically, this prolific deposit is hosted within Carboniferous-age limestones and overlying Permo-Triassic sedimentary sequences. Mineralization occurred when highly saline, deep-seated basinal brines mixed with cooler, low-salinity meteoric or evaporated seawater fluids along active fault conduits during Late Triassic to Late Jurassic rifting events associated with the opening of the Atlantic Ocean. This process precipitated high-purity fluorite within extensive vein networks and stratabound replacement bodies, with the mineral developing inside large open cavities as magnificent, razor-sharp cubic crystals that display breathtaking sky-blue, lavender, and deep purple geometric color zoning, often growing as terraced, stepped, or multi-crystalline groups sitting on a contrasting matrix of white calcite or pale barite. Historically, while initial fluorite discoveries in the La Collada area date back to 1904 during regional railway construction, systematic surface quarrying and underground mining at the La Viesca claim were initiated in 1945 by the corporate operator La Audacia Minera. The mine went through several phases of intensive industrial development to supply commercial fluorspar flux to global metallurgical industries, experiencing a highly celebrated golden era for specimen recovery from the late 1970s through the early 1980s, and continuing to produce legendary world-class pockets, such as the famous Las Monjas pocket discovered as late as May 2010. Commercial and specialized extraction at the underground workings eventually ceased, leaving the mine closed and inaccessible through 2026, though original early-era and modern-era La Viesca blue fluorite clusters remain intensely sought after by advanced collectors and museums for their pristine clarity, intense color saturation, and classic Spanish provenance.

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