Bayldonite

Bayldonite
Bayldonite, Tsumeb, Namibia
General
CategoryArsenate minerals
Formula
(repeating unit)		PbCu3(AsO4)2(OH)2
IMA symbolBay[1]
Strunz classification8.BH.45
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupC2/c
Identification
ColorGreen, apple-green
Crystal habitMammillary crust
TwinningPseudoscalenohedral trillings with the composition plane
CleavageNone observed
FractureIrregular/uneven, conchoidal, sub-conchoidal, fibrous
TenacityBrittle
Mohs scale hardness4+1⁄2
LusterResinous, waxy, greasy
StreakSiskin green to apple green
DiaphaneityTransparent, translucent
Density5.24–5.65 g/cm3 (measured), 5.707 g/cm3 (calculated)
Optical propertiesBiaxial (+)
Refractive indexnα = 1.951 nβ = 1.970 nγ = 1.991
Birefringence0.040
PleochroismNon-pleochroic
2V angle89°
Dispersionr < v strong
ExtinctionY^elongation = 45°; X=b
References[2][3][4]

Bayldonite (BAIL-done-ite)[5] is a rare secondary mineral with the chemical formula PbCu3(AsO4)2(OH)2. Its provenance has been attributed to Penberthy Croft Mine, Cornwall, England, United Kingdom but there is no substantiating evidence for this and it was only attributed to Cornwall by Church (1865). Also, Church’s paper (Church, 1865) clearly states “I am indebted to Mr. Talling for this mineral species also.” so the original material was supplied by the mineral dealer Richard Talling and not discovered by Bayldon. [6][5] Bayldonite was named after Church's dear friend and colleague at the Royal Agricultural College (RAC),Cirencester, Gloucestershire John Bayldon MD (1837 – 1872).[7] Specimens are also found in Tsumeb, Namibia, and Arizona, United States. It is sometimes used as a gemstone.[8]

References

Wikimedia Commons has media related to Bayldonite.
  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ Mineralienatlas
  3. ^ "Bayldonite Mineral Data". Webmineral. Archived from the original on 7 June 2011. Retrieved 6 June 2011.
  4. ^ "Bayldonite mineral information and data". Mindat. Retrieved 6 June 2011.
  5. ^ a b Thomas, Arthur (2008). Gemstones: properties, identification and use. New Holland Publishers. p. 159. ISBN 978-1-84537-602-4.[permanent dead link‍]
  6. ^ A. H. Church: XLI.—Chemical researches on some new and rare cornish minerals. In: Journal of the Chemical Society, 1865, 18, S. 259-268, doi:10.1039/JS8651800259.
  7. ^ A. H. Church: XLI.—Chemical researches on some new and rare cornish minerals. In: Journal of the Chemical Society, 1865, 18, S. 259-268, doi:10.1039/JS8651800259.
  8. ^ Gemstones: Properties, Identification and Use By Arthur Thomas, p.159


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