Carlosturanite (Not ‘Picrolite’) from Taberg, Sweden

Marcello Mellini and Jack Zussman
C.N.R., C.S. Geologia Strutturale Dinamica dell'Appennino, via S. Maria 53, 56100 Pisa, Italy
Department of Geology, University of Manchester, Oxford Road, Manchester M13 9PL, UK

Abstract: The second occurrence of the asbestiform silicate carlosturanite is reported. The mineral occurs in Taberg, Sweden, and it was previously reported as ‘picrolite’, that is fibrous antigorite. Carlosturanite from Taberg is non-pleochroic, green in colour and has positive optical elongation. The unit cell parameters are a = 36.55, b = 9.31, c = 7.27Å, β = 101.05°. Based on the determined formula, (Mg20.47Fe0.59Mn0.06Cr0.01Ti0.01) (Si11.68Al0.28)O27.81(OH)34.19H2O carlosturanite can be expected to crystallize within the pure MgO-SiO2-H2O system as a low-grade metamorphic mineral.

Because there are close similarities in structure and properties of carlosturanite and the picrolite variety of antigorite, their distinction requires careful attention to X-ray and electron diffraction patterns and chemical compositions. The present identification of the Taberg specimen as carlosturanite puts a lower limit of 33.7 Å to the known range of a parameters of antigorite.

Keywords: carlosturanite • picrolite • antigorite • asbestiform minerals • Taberg • Sweden

Mineralogical Magazine; December 1986 v. 50; no. 358; p. 675-679; DOI: 10.1180/minmag.1986.050.358.14
© 1986, The Mineralogical Society
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