Abstract

Kellyite, (Mn3Mg0.5Fe3+0.2Al1.7)(Si2.0AL2.0)O10(OH)8, occurs as transparent, yellow, I mm-sized grains dispersed within manganese carbonates (principally kutnahorite) at the Bald Knob manganese mine, near Sparta, North Carolina. Associated minerals include galaxite, jacobsite, Mn-chlorite, alleghanyite, and sonolite. X-ray diffraction shows that it is isostructural with members of the serpentine group and thus the manganese equivalent of amesite. Two polytypes have been recognized, a six-layer rhombohedral phase and a twd-layer hexagonal phase. The latter has space group P68, and lattice parameters a = 5.438 ± 0.008 Å and c = 14.04 ± 0.01 Å. The name is in honor of William C. Kelly, faculty member of the Department of Geology and Mineralogy, The University of Michigan.

A mineral which yields a powder pattern identical to that of grovesite occurs with the kellyite. It is shown to be a one-layer chlorite having space groupCl or Cl, with lattice parameters a= 5.44Å, b = 9.40Å, c = 14.27A Å, α= γ=90.0°, and β = 98°.12'. It is proposed that grovesite, formerly classed as a rnember of the serpentine group, is actually a manganese chlorite which is chemically similar to pennantite.

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