Madocite

Pb17(Sb,As)16S41IMA symbolMdc[1]Strunz classification2.LB.30Crystal systemOrthorhombicCrystal classPyramidal (mm2)
(same H-M symbol)Space groupPb2aUnit cella = 27.2  Å, b = 34.1 Å,
c = 8.12 Å; Z = 4IdentificationColorGrayish blackCrystal habitElongated and striated crystals; massiveCleavage{010} PerfectFractureConchoidalMohs scale hardness3.25LusterMetallicStreakGrayish black, shiningDiaphaneityOpaqueSpecific gravity5.98PleochroismStrong, from white to grayReferences[2][3][4][5][6]

Madocite is a mineral with a chemical formula of Pb17(Sb,As)16S41. Madocite was named for the locality of discovery, Madoc, Ontario, Canada. It is found in the marbles of the Precambrian Grenville Limestone.[6] It is orthorhombic (rectangular prism with a rectangular base) and in the point group mm2. Its crystals are elongated and striated along [001] to a size of 1.5 mm.

Madocite is anisotropic and classified as having high relief. It also displays strong pleochroism.[5]

Madocite is found in small clusters in marble pits (near Madoc, Ontario), and was originally categorized in the 1920s as an unidentified sulfosalt mineral in an assemblage of pyrite, sphalerite, and jamesonite in marble. Later research was done by John L. Jambor in the 1960s who went to the site and collected samples of the assemblages.[7]

References

  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. ^ Mindat.org
  4. ^ (1968) American Mineralogist, 53, 1421
  5. ^ a b Webmineral data
  6. ^ a b Anthony, J. W., Bideaux, R. A., Bladh, K. W., and Nichols, M. C. (1990) Handbook of Mineralogy: Volume 1: Elements, Sulfides, Sulfosalts. 306 p. http://rruff.geo.arizona.edu/doclib/hom/madocite.pdf
  7. ^ History of discovery


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