Dumortierite

specimen number:
2262251

location:
Lincoln Hill, Pershing Co., Nevada, USA

description:
Light bluish gray crystalline dumortierite throughout matrix.

The Lincoln Hill dumortierite locality, positioned on the western ridge bounding Rochester Canyon within the Rochester mining district of Pershing County, Nevada, is a premier American locality celebrated for producing massive aggregates of highly distinctive pink, lavender, and deep blue dumortierite. Geologically, this extraordinary deposit is hosted within the Early Triassic-age Rochester Formation, which is dominated by highly altered felsitic trachyte breccias and rhyolitic tuffs that underwent intense, localized hydrothermal metamorphism during the late Jurassic plutonic intrusions. Ascending boron- and aluminum-rich hydrothermal fluids extensively shattered the trachyte host rock, creating an immense, interlaced network of quartz veins and mineralized fractures where the rare aluminum borosilicate, dumortierite, precipitated alongside quartz, sericite, andalusite, and accessory tourmaline, giving the resulting dumortierite-sericite schist its striking coloration and dense, fine-grained texture. Historically, precious metal veins were first discovered nearby in the early 1860s, but the immense Lincoln Hill dumortierite mass was formally documented during a geological reconnaissance in 1913 following a massive regional silver boom. While small-scale surface quarrying and trenching for mineral specimens occurred sporadically from 1913 through the 1920s, the property saw a unique phase of industrial development in the late 1920s and 1930s when the Champion Spark Plug Company acquired claims in Limerick Canyon and Lincoln Hill to mine the massive, high-aluminum dumortierite rock for use in manufacturing specialized, high-temperature automotive spark plug ceramics.

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