Alstonite , Witherite Locality: Brownley Hill Mine (Bloomsberry Horse Level), Nenthead , Alston Moor District, North Pennines , North and Western Region (Cumberland), Cumbria , England , UK ( Locality at mindat.org ) Size: small cabinet, 9.7 x 4.1 x 3.7 cm Alstonite with Witherite This rich specimen dates back to , I would expect, the heyday here in the mid-1800s. It is covered by very sharp, alstonites to 6mm. Atop is a 2-cm cluster of witherite, as well. I think the orange dot atop is the remnant of a very old glue label. In any case, its surprisingly an attractive specimen, although there is some value to the even more attractively prepared, and exhaustively descriptive, old labels! — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Alstonite
A rare double carbonate of barium and calcium (sometimes with strontium) deposited by low-temperature hydrothermal fluids.
Intro adapted from Wikipedia (CC BY-SA).
Alstonite is an IMA-recognized mineral species in the carbonate class, with the chemical formula BaCa(CO₃)₂.
It crystallizes in the orthorhombic crystal system (space group C-1). It is a member of the Alstonite structural group.
Key properties: Mohs hardness 4–4.5; specific gravity 3.707; White streak; Vitreous luster; optically biaxial.
IMA symbol Asn, grandfathered status — known before the IMA’s founding, named in 1841.
is typically found in low-temperature hydrothermal Pb–Zn deposits; rare in carbonatites.
It is found associated with Calcite, barite, ankerite, siderite, benstonite, galena, sphalerite, pyrite, quartz.
The name refers to the original locality near Alston, England.