"Rock of the Month # 287, posted for May 2025" ---

Anglesite (PbSO₄)

is an orthorhombic sulphate of lead, a secondary mineral typically formed from primary mineralization in the form of galena (PbS), the familiar cubic sulphide. The mineral is named for its type locality, the ancient Parys Mountain mine on the island of Anglesey in northwest Wales.

Although anglesite tends to be a rather low-key mineral, it is widely distributed, including occurrences in: the U.S.A. (CA, ID, AZ, NV, CO, MT, TN, PA); Canada (B.C., Yukon, Newfoundland); Mexico (Chihuahua, Coahuila, Michoacan); the British Isles (Scotland, England, Ireland) and elsewhere in Europe; Morocco; Iran (Wilson, 2023); India; and Australia.

While primary ores of lead and zinc are economically dominated by a very few ore minerals, galena and sphalerite in particular, oxidized deposits can also be important, and also carry additional metals of value, silver included. Supergene weathering of Pb deposits produces a variety of secondary minerals of lead, such as cerussite, anglesite, massicot and pyromorphite (Emmons, 1917). Furthermore, the weathering of historical smelter slags can result in a mix of primary (e.g., galena) and secondary minerals, such as litharge, hydrocerussite, cerussite, leadhillite and anglesite (Gee et al., 1997).

Boyle (1960) described the occurrence of native Ag in the Keno Hill- Galena Hill area of the Yukon, Canada, in deeply oxidized lodes, unusual for Canada, containing also other minerals such as galena, anglesite and cerussite. Some of these secondary minerals furnished specimens for early mineral dealers, the offerings including cerussite and hemimorphite from Roughton Gill (English Lake District), and anglesite from Anglesey (Cooper et al., 2009).

More occurrences

In the case of this sample, "Joplin" may be a rather generic, district-scale location reference. The carbonate (limestone) - hosted lead-zinc deposits of the Ozark region have been worked and studied for over a century (Bain, 1901; Stinchcombe, 2014), with deposits scattered across Missouri and northern Arkansas. Galena, sphalerite and smithsonite are the important ore minerals. The wider Tri-State mining district encompasses parts of Missouri, Kansas and Oklahoma and was a major Pb-Zn producer from 1850 to 1950, with over 4,000 mines beneath a 2,000 square mile (5,180 km²) area of southwest Missouri, southeast Kansas and northeast Oklahoma: over 60 mineral species are reported from the region, including anglesite and galena (Bicknell and Wilson, 2017). Joplin has yielded a range of mineral species besides anglesite, notably including calcite and galena, sphalerite and hemimorphite, marcasite and greenockite. An early, detailed review of dolomitization gives many examples, including around Pb-Zn ores of the Joplin district and the Leadville Formation, Aspen area, Colorado (van Tuill, 1914).

Other North American examples are well-known and widespread. In the Darwin district, Inyo county, California, there are granitoids and skarns, and Ag values in Pb ores, containing galena, cerussite and anglesite (Knopf, 1914). Even earlier, Benjamin Silliman (1873) reported compact anglesite at the Union mines near Cerro Gordo in Inyo county. The Eureka district in Nevada was discovered in 1864, and produced some 1.65 million ounces of Au, most of it between 1870 and 1890. Rich, oxidized bonanza ores near the surface contained minerals such as Fe oxides, native Au, anglesite, cerussite, mimetite, plumbojarosite and bindheimite (Shawe and Nolan, 1989). The carbonate replacement Pb Zn Ag deposits of Mexico were mostly discovered in outcrop more than 100 years ago, and most were oxidized to depth. The oxidized manto and chimney deposits were exploited as compact bodies of Ag -rich cerussite and anglesite, while associated oxide zinc mineralization was mostly ignored until later (Megaw, 2009).

In the British Isles, anglesite is reported from the Leadhills-Wanlockhead district of Scotland (Gillanders, 1981; Livingstone, 1993). A radium-bearing variant was described in Cornwall (Harrison and Taylor, 1966). At the type locality, the Parys Mountain mine in Anglesey, the sulphate is found as attractive pale, orange-tinged crystals, anglesite samples in prominent collections, such as those of Sir Arthur Russell and the Natural History Museum in London (Plant et al., 2011). It occurs also at a noted fluorite locality in county Galway, Ireland (Sweeney and Unitt, 2011).

REFERENCES

Bain,HF (1901) Preliminary report on the lead and zinc deposits of the Ozark region. USGS 22nd Annual Report, Part II - Ore Deposits, 23-227.

Bicknell,D and Wilson,WE (2017) The Tri-State mining district, Missouri- Kansas- Oklahoma. Mineralogical Record 48 no.2, 181-276.

Boyle,RW (1960) Occurrence and geochemistry of native silver in the lead-zinc-silver lodes of the Keno Hill-Galena Hill area, Yukon, Canada. NJFM 94 (Ramdohr volume), 280-297.

Cooper,MP, Wilson,WE and Wilson,ML (2009) Famous mineral dealers: Bryce McMurdo Wright, Sr. (1814-1875) and Bryce McMurdo Wright, Jr. (1850-1895). Mineralogical Record 40, 445-466.

Emmons,WH (1917) The Enrichment of Ore Deposits. USGS Bull. 625, 530pp.

Gee,C, Ramsey,MH, Maskall,J and Thornton,I (1997) Mineralogy and weathering processes in historical smelting slags and their effect on the mobilisation of lead. J.Geochem.Explor. 58, 249-257.

Gillanders,RJ (1981) Famous mineral localities: the Leadhills-Wanlockhead district, Scotland. Mineralogical Record 12 no.4, 235-250.

Harrison,RK and Taylor,K (1966) Radian anglesite from Wheal Speed, Cornwall. Bull.Geol.Surv.G.B. 25, 41-48.

Knopf,A (1914) The Darwin silver-lead mining district, California. USGS Bull. 580-A, 18pp.

Livingstone,A (1993) Glossary of Scottish mineral species - an update. Scot.J.Geol. 29, 87-101.

Megaw,PKM (2009) Evaluation of oxidized Pb-Zn-Ag carbonate replacement deposits of Mexico in light of supergene zinc and residual lead enrichment processes. In `Supergene Environments, Processes, and Products' (Titley,SR editor), SEG Spec.Publ. 14, 149pp., 51-58.

Plant,SP, Cotterell,TF and Starkey,RE (2011) Anglesite from the type locality, Parys Mountain, Anglesey, Wales. Mineralogical Record 42, 345-384.

Shawe,DR and Nolan,TB (1989) Gold in the Eureka mining district, Nevada. USGS Bull. 1857-C, 47pp., 27-37.

Silliman,B (1873) Mineralogical notes on Utah, California and Nevada, with a description of priceite, a new borate of lime. Amer.J.Sci. 106, 126-133.

Stinchcombe,BL (2014) Mineral Treasures of the Ozarks. Schiffer Publishing, 160pp.

Sweeney,M and Unitt,R (2021) Larkin's quarry, Connemara, Ireland. Mineralogical Record 52 no.2, 129-156.

van Tuyl,FM (1914) The origin of dolomite. Iowa Geological Survey Annual Report 25, 251-422.

Wilson,WE (2023) The Nakhlak mine, Anarak district, Esfahan province, Iran. Mineralogical Record 54 no.3, 383-408.