Wiktionary
barstowite
n. (context mineral English) A transparent to white monoclinic halide mineral.
Wikipedia
Barstowite
Barstowite, formula Pb[Cl|CO]•HO, is a transparent to white mineral in the monoclinic system. It has a Mohs hardness of 3, a white streak and an adamantine lustre.
The type locality for Barstowite is Bounds Cliff, St Endellion, Cornwall in the United Kingdom. It is named after Richard W. Barstow (1947–1982) a Cornish mineral collector.