Lautenthalite

Crystal System: Monoclinic
Status of Occurrence: Confirmed Occurrence
Distribution: Rare
Chemical Composition: Lead copper hydroxide sulphate hydrate
Chemical Formula: PbCu4[(OH)6(SO4)2].3H2O
Method(s) of Verification: Cwmystwyth - EDX (Rust & Green, in prep); Frongoch - EPMA (Green et al., 1996); Penrhiw - EPMA (Mason & Green, 1995); Darren, Dylife, Esgair Hir, Hendrefelen & Eaglebrook all by XRD at NHM (XRD nos. 7691F, 5146F, 6762F, 8145F & 4472F respectively).

Chemical Group:

  • Sulphates

Geological Context:

  • Supergene: post-mining oxidation & weathering deposits
  • Supergene: minerals on an artificial substrate
Introduction: a supergene mineral that typically forms during the oxidation of copper, lead and zinc sulphides in mine spoil. Lautenthalite is frequently observed in association with wroewolfeite, which it tends to overgrow.
Occurrence in Wales: lautenthalite, the lead analogue of devilline was first described from old smelt slag from Lautenthal, Germany in 1993 but the mineral that was to be named as lautenthalite had, previously been found in slag from the Meadowfoot Smelter, Wanlockhead, Scotland (Green, 1987). The first ‘natural’ occurrences of lautenthalite from the British Isles are from Wales, in weathered veinstone from a number of mines, all in the Central Wales Orefield. Many of these occurrences had been noted prior to the formal naming of lautenthalite in 1993. Although occurring only as microcrystals, lautenthalite has been recorded from many localities within the Central Wales Orefield typically, of post-mining origin through the weathering of mine spoil. Indeed, to date almost all of the natural occurrences of lautenthalite worldwide are from minesites within Central Wales (Rust & Green, in prep).

Key Localities:

  • Brynyrarian Mine, Tre-Taliesin, Ceredigion: lautenthalite has been identified on a small number of specimens collected from the dumps, where it appears to have formed by recent oxidation of sulphide-bearing vein material. The mineral occurs as groups of radiating, emerald-green, bladed, to prismatic crystals (up to 2 mm), associated with anglesite, linarite, schulenbergite, ramsbeckite, langite and hemimorphite (Rust & Green, in prep.).
  • Cwmystwyth Mine, Cwmystwyth, Ceredigion: lautenthalite is recorded underground in the Copper Level, as transparent, green, pointed to tabular crystals (up to 0.5 mm in length) intimately associated with wroewolfeite in a brecciated quartz vein. The vein also contains partially oxidized chalcopyrite and galena (Rust & Green, in prep.).
  • Darren Mine, Pen-bont Rhydybeddau, Ceredigion: three specimens collected in 1989 from a small ore pile outside the Darren Fach adit display radiating aggregates of light emerald-green crystals up to 0.6 mm in size (Rust & Green, in prep.). These are associated with caledonite, hydrocerussite and langite.
  • Dylife Mine, Penegoes, Powys: Rust & Rust (1987) described lautenthalite from Dyfngwm Mine, although the collecting site is actually at mine dumps near the westernmost boundary of Dylife Mine. The lautenthalite forms isolated, green, bladed crystals or crystal groups up to 1 mm in size, associated with anglesite, bechererite, cerussite, langite, linarite, schulenbergite, ramsbeckite, and susannite (Rust & Green, in prep.).
  • Eaglebrook (Nantycagl) Mine, Ceulanymaesmawr, Ceredigion: the mineral now known as lautenthalite was, initially collected from the eastern shaft dump in 1984 by P. Wallace. Lautenthalite was relatively common at this site forming emerald green subparallel crystal groups to 2 mm and as orientated overgrowths around prismatic wroewolfeite. Typical associates include anglesite, linarite, and cerussite, and more rarely brochantite, caledonite, cuprite, hemimorphite, langite, leadhillite, and serpierite (Rust & Green, in prep.).
  • Esgairhir Mine, Tal-y-bont, Ceredigion: lautenthalite forms broad curved platy crystals (exceptionally up to 1.5 mm) in aggregates on specimens collected from the dump next to the ruined engine house (Rust & Green, in prep.). Typical associated species include brochantite, cerussite, langite, linarite, susannite, and wroewolfeite.
  • Frongoch Mine, Devil's Bridge, Ceredigion: very rare emerald-green, tabular to bladed crystals (up to 0.7 mm in size) occur associated with wroewolfeite, brochantite, and linarite on cerussite overgrowing goethite-coated quartz. Occasionally the lautenthalite forms epitaxial overgrowths on wroewolfeite (Green et al., 1996).
  • Hendrefelin Mine, Ysbyty Ystwyth, Ceredigion: lautenthalite occurs as broad tapering green tabular crystals in oxidized sulphide-rich matrix on the most westerly dump (Rust & Green, in prep.). Lautenthalite is known to overgrow wroewolfeite from Hendrefelen, and is associated with langite, caledonite, susannite, linarite, cerussite, and brochantite.
  • Penrhiw Mine, Ystumtuen, Ceredigion: recorded on a few specimens, lautenthalite is typically associated with wroewolfeite. It forms minute, emerald-green crystals which occur as isolated blocky crystals, or more typically thin tabular crystals associated with with wroewolfeite, and rarely in epitaxial overgrowth on wroewolfeite (Mason & Green, 1995).

References:

  1. Bevins, R.E. & Mason, J.S., 1997. Welsh metallophyte and metallogenic evaluation project: Results of a minesite survey of Dyfed and Powys. CCW Contract Science Report No. 156. National Museums & Galleries of Wales.
  2. Green, D.I., 1987. The Minerals of Meadowfoot Smelter. UK Journal of Mines and Minerals, 2, 3-9.
  3. Green, D.I., Rust, S.A. & Mason, J.S., 1996. Classic British mineral localities: Frongoch Mine, Dyfed. UK Journal of Mines & Minerals, 17, 29-38.
  4. Mason, J.S. & Green, D.I., 1995. Supergene minerals including exceptional ramsbeckite from Penrhiw Mine, Ystumtuen, Dyfed. UK Journal of Mines & Minerals, 15, 21-27.
  5. Medenbach, O., & Gebbert, W., 1993. Lautenthalite, PbCu4[(OH)6/(SO4)2].3H2O, the Pb analogue of devellite – A new mineral from Harz mountains, Germany. Neues Jahrbuch für Mineralogie, Monatshefte, 401-407.
  6. Rust, S. & Rust, D., 1987. Micro-minerals from Dyfngwm Mine. U.K. Journal of Mines and Minerals, No. 2, 28-32.
  7. Rust, S.A. & Green, D.I., (in prep.). The occurrence of lautenthalite in the British Isles. UK Journal of Mines and Minerals.