Bayldonite

Bayldonite (BAIL-done-ite)[4] is a rare secondary mineral with the chemical formula PbCu3(AsO4)2(OH)2. It was first discovered in Penberthy Croft Mine, Cornwall, England, United Kingdom.[4] It is named after its discoverer, John Bayldon (1837(8) – 1872).[5] Specimens are also found in Tsumeb, Namibia, and Arizona, United States. It is sometimes used as a gemstone.[6]

Bayldonite
Bayldonite-Malachite-160206.jpg
Bayldonite, Tsumeb, Namibia
General
CategoryArsenate minerals
Formula
(repeating unit)
PbCu3(AsO4)2(OH)2
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+12
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[1][2][3]

ReferencesEdit

  1. ^ Mineralienatlas
  2. ^ "Bayldonite Mineral Data". Webmineral. Archived from the original on 7 June 2011. Retrieved 6 June 2011.
  3. ^ "Bayldonite mineral information and data". Mindat. Retrieved 6 June 2011.
  4. ^ a b Thomas, Arthur (2008). Gemstones: properties, identification and use. New Holland Publishers. p. 159. ISBN 978-1-84537-602-4.
  5. ^ 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.
  6. ^ Gemstones: Properties, Identification and Use By Arthur Thomas, p.159