Barstowite

{{Short description|Mineral}}

{{Use dmy dates|date=April 2022}}

{{Infobox mineral

| name = Barstowite

| category = Halide minerals

| image = Barstowite-90280.jpg

| imagesize = 260px

| alt =

| caption = Barstowite from Passa Limani area, Lavrion District, Attiki Prefecture, Greece

| formula = Pb₄[Cl₆|CO₃]•H₂O

|IMAsymbol=Bsw{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}

| molweight =

| strunz = 3.DC.95

| system = Monoclinic

| class = Prismatic (2/m)
(same H-M symbol)

| symmetry = P2₁/m

| color = White to transparent

| habit =

| twinning =

| cleavage =

| fracture =

| tenacity =

| mohs = 3

| luster = Adamantine

| polish =

| refractive =

| opticalprop =

| birefringence =

| dispersion =

| pleochroism =

| fluorescence=

| absorption =

| streak = White

| gravity =

| density =

| melt =

| fusibility =

| diagnostic =

| solubility =

| diaphaneity =

| other =

| references =

}}

Barstowite, formula Pb₄[Cl₆|CO₃]•H₂O, is a transparent to white mineral in the monoclinic system.[http://www.mindat.org/min-540.html Barstowite at Mindat.org mineralogical website] 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.{{Cite web |url=http://www.minrec.org/labels.asp?colid=103 |title=Mineralogical Record article on Richard Barstow |access-date=2008-01-05 |archive-url=https://web.archive.org/web/20080921194423/http://www.minrec.org/labels.asp?colid=103 |archive-date=2008-09-21 |url-status=dead }}