Type Locality
There are two type localities, both in the north of England. One is the Brownley Hill Mine (Bloomsberry Horse Level), Nenthead, Alston Moor District, North Pennines, Cumbria, and the other is the Fallowfield Mine, Acomb, Hexham, Tyne Valley, Northumberland. The type material is held at the Freiberg Mining Academy, Germany, 15818.
At the type locality at Brownley Hill, alstonite occurs in low-temperature lead-zinc hydrothermal deposits associated with witherite, calcite and baryte. The crystals are white to colourless or faintly pink acute pseudohexagonal pyramids or dipyramids up to 6 mm long. In some specimens the alstonite is intergrown with very thin hexagonal platy crystals of nailhead calcite. Alstonite commonly encrusts compact crystalline white to pale pink baryte. Similar crystals have been found at Fallowfield. It occurs typically in low-temperature hydrothermal lead-zinc ore deposits, as is the case at the type localities, and it has also been reported as a rare phase in carbonatites. It occurs associated with calcite, baryte, ankerite, siderite, benstonite, galena, sphalerite, pyrite and quartz.
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