Alstonite
specimen number:
2102305
location:
Brownley Hill Mine, Alston Moor, Cumbria, England, UK
description: The Brownley Hill Mine, located near Nenthead in the Alston Moor District of Cumbria, England, is a classic locality within the Northern Pennine Orefield. Geologically, the mine worked a series of hydrothermal veins hosted in Carboniferous limestones and sandstones, where mineralizing fluids deposited lead and zinc sulfides alongside a suite of rare carbonates. The site is world-famous for its specimens of alstonite, a rare barium calcium carbonate mineral that is dimorphous with barytocalcite. Alstonite typically occurs at this locality as small, colorless to white, steeply bipyramidal crystals that often exhibit complex twinning, forming sharp, pseudo-hexagonal groupings within the weathered portions of the veins. Historically, the mine was developed primarily for lead and later zinc, with significant underground mining and quarrying activities recorded from the late 18th century through the mid-20th century. Major periods of operation were managed by the London Lead Company and the Vieille Montagne Zinc Company, with peak production occurring in the 1800s before the mine finally closed in the 1930s. Today, Brownley Hill is revered by mineralogists for its high-quality carbonate species and its historical contribution to the understanding of the unique mineralogy of the North Pennines.
A choice for the species, colorless scalenohedral crystals of alstonite to 0.3 cm in size quite rich across the top of matrix. In good condition.
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