Madocite Explained

Madocite
Category:Sulfosalt mineral
Imasymbol:Mdc[1]
Strunz:2.LB.30
System:Orthorhombic
Class:Pyramidal (mm2)
(same H-M symbol)
Symmetry:Pb2a
Unit Cell:a = 27.2  Å, b = 34.1 Å,
c = 8.12 Å; Z = 4
Color:Grayish black
Habit:Elongated and striated crystals; massive
Cleavage: Perfect
Fracture:Conchoidal
Mohs:3.25
Luster:Metallic
Pleochroism:Strong, from white to gray
Streak:Grayish black, shining
Gravity:5.98
Diaphaneity:Opaque
References:[2] [3] [4] [5] [6]

Madocite is a mineral with a chemical formula of . 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]

Notes and References

  1. Warr. L.N.. 2021. IMA–CNMNC approved mineral symbols. Mineralogical Magazine. 85. 3. 291–320. 10.1180/mgm.2021.43. 2021MinM...85..291W. 235729616. free.
  2. https://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Madocite Mineralienatlas
  3. http://www.mindat.org/min-2517.html Mindat.org
  4. (1968) American Mineralogist, 53, 1421
  5. http://webmineral.com/data/Madocite.shtml Webmineral data
  6. 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. http://www.corpusetampois.com/cse-guettardite.html History of discovery