MINERAL-D 

(Fe³⁺-Mg-Mn-arsenite-arsenate?)

	Figure 26-1. Rosette of curved platy crystals of Mineral-D from Sterling Hill. Field of view is  0.3 mm in maximum dimension.

Mineral-D, a ferric-iron analogue of hematolite from Sterling Hill, was described by Dunn and Peacor (1983b). It occurs as 1-2 mm semispherical aggregates of hexagonal platy crystals (Figure 26-2) and as ragged-edge platy aggregates (Figure 26-1). The color is reddish brown; the mineral resembles mcgovernite or kraisslite, but is slightly redder. Single-crystal X-ray investigations showed that the mineral has a = 8.28 Å, but that the value of c could not be determined with reliability. Intense diffractions define a cell with c = 72.69 Å, but other diffractions define a cell with c = 48.46 Å. The structure has a basic repeat unit of 12.2 Å along c; hematolite has c = 36.6 Å. This Sterling Hill mineral, although different compositionally from hematolite, is based on the same basic structural unit, with different polytypic stacking sequences.

	Figure 26-2. Cluster of platy hexagonal crystals of Mineral-D from Sterling Hill. Field of view is 0.4 mm in maximum dimension.

Microprobe analyses of two specimens from Sterling Hill yielded: Al₂O₃ 0.8, 0.0, Fe₂O₃ 8.1, 9.2, MgO 12.7, 5.7, ZnO 5.8, 7.8, MnO 39.0, 45.8, As₂O₅ 14.5, 14.0, As₂O₃ 6.2, 6.0, H₂O (by difference) 12.9, 11.5, total = 100.0, 100.0 wt. %; the first- given water value corrects an error in the original paper. This hematolite-like mineral occurs with chlorophoenicite, barite, franklinite, willemite, and retzian-(Nd). It also occurs separately with allactite and altered covelline. Mineral-D has not been found at Franklin. The reader is referred to Dunn and Peacor (1983b) for a more extensive discussion and data on specimens from Långban, Sweden.

Copyright © 1995 by Pete J. Dunn			Website by Herb Yeates
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This page created: January 11, 2001