112g fluorite skull – Collector's Piece – Georgian craft...

In England in the 18th century, a particular fluorite variety, blue-violet to yellow banded, from the Castleton caves in Derbyshire, was regarded as one of the era's most coveted materials — called "Blue John." The manufacturer Matthew Boulton had sumptuous vases and candelabra turned from it from the 1760s onward in his Soho Manufactory in Birmingham, which stood in the salons of the nobility. What gleamed in the stately houses, however, concealed a craftsman’s secret that the turners guarded closely: the material cleaves along its perfect octahedral cleavage so easily that raw fluorite hardly ever came out of the rock without internal fractures. Before any turning could even take place, the rough piece had to be impregnated and stabilized with resin — a process the workshops of the time treated as a trade secret, because without it hardly any piece would survive the cut. Exactly this property is also contained in this skull, but entirely without any workshop intervention: the finely, in many places fractured semi-transparency inside is not a flaw but the visible trace of countless tiny, naturally flowing fracture planes that refract light multiple times before it exits again — a "Crushed" effect that arises precisely from that crystallographic property which even the Georgian turners drove to despair. Even the surface, which remains perceptibly rough despite polishing, can be explained by this: where such an internal fracture plane runs just beneath the surface, it can never be polished completely smooth, but stays perceptible, almost like an old scar beneath the skin. Mineralogically, fluorite is calcium fluoride (CaF₂), whose strong color banding — here a cool, sea-water blue-green beside cream to yellowish zones — results from color centers caused by natural radiation as well as the finest impurities in the crystal lattice. Material: Fluorite (calcium fluoride, CaF₂) Origin: Brazil Dimensions: 5.1 x 3.4 x 3.6 cm Weight: 112 g Special features: Pronounced internal fracture/cleavage structure with "Crushed" optics due to natural octahedral cleavage; still perceptibly rough surfaces after polishing; cool blue-green cream-toned banding

Estimate:£127.53

View all items fromCatawikiorEthnographical