Ilvaite

specimen number:
1052752

location:
Koundouros, Serifos Island, Milos, South Aegean, Greece

description:

Excellent example for the species from this Greek locality, a grouping of thick mostly lustrous terminated ilvaite crystals. In good condition all around. The specimen comes with an antique label as shown at the end of the video. The label provides an original acquisition date in 1928.

The Koundouros mining area, situated on the southwestern coast of Serifos Island in the Cyclades, Greece, was a significant historical source of high-grade iron ore. Geologically, the deposit is a world-class distal iron skarn system formed during the Miocene epoch when an I-type granodiorite pluton intruded into the Attic-Cycladic Crystalline Belt, cooking the surrounding marbles and schists. This intense contact metamorphism and subsequent retrograde hydrothermal alteration created massive zones of calcium-iron silicates, specifically hedenbergite pyroxene, which was progressively replaced by a highly specialized mineral assemblage. Within the cavities and geodes of this skarn matrix, fluids rich in iron, calcium, and silica precipitated large, lustrous, idiomorphic crystals and radial aggregates of ilvaite, which reached lengths up to 50 centimeters and occurred in close association with prase quartz, calcite, and lamellar hematite. Historically, while artisanal mining on Serifos dates back to antiquity around 3000 BC, industrial-scale underground shaft sinking and open-cut quarrying at Koundouros boomed in the late nineteenth century under commercial entities like the French company Societe des Mines de Serifos. Large-scale extraction of the rich magnetite and hematite ores peaked between the 1880s and the outbreak of World War I, after which labor unrest, falling iron prices, and ore depletion caused a steady decline, culminating in the permanent cessation of all commercial mining operations by the mid-twentieth century.

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