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(Mn,Mg)4(Zn,Mg)3(CO3)2(OH)10
Monoclinic, A2/a, a = 16.408, b = 5.540, c
= 15.150 Å,
b = 95.48o, Z = 4
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| Figure 23-22. Crystal drawings of loseyite from Franklin; these drawings are two projections (A and B) of one crystal. Drawings are from Palache (1935) who provided crystallographic data. | ||
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Loseyite was first described from Franklin by Bauer and Berman (1929a, 1929c); it has not been found since at either deposit. Unit-cell parameters were described by Wolfe and Frondel (Palache et al., 1951).
The crystal structure was described by Hill (1981), who reported it to have a regularly stepped sheet of edge- and corner-sharing manganese octahedra. A vacant octahedral site in this sheet shares its upper and lower faces with tetrahedral [ZnO(OH)3] groups.
Carbonate groups are on opposite sides of the sheets, and oriented normal to them. Compare the isostructural mineral, sclarite, which has octahedral and tetrahedral zinc.
Loseyite occurs as sharp blue-white to colorless, lath-shaped crystals which were illustrated by Bauer and Berman (1929) and Palache (1935) (Figure 23-22). The luster is vitreous, cleavage is absent or unobserved, and the density is 3.27 g/cm3 (Bauer and Berman, 1929), 3.25 g/cm3 (present study). Optically, loseyite is biaxial, positive, 2V = 64o, with a = 1.637, b = 1.648, and g = 1.676; the orientation is Y = b; dispersion is r > v, weak. The fluorescence in ultraviolet is unrecorded; given the Mn-content, it might be absent.
Loseyite is a manganese zinc carbonate hydroxide mineral. The analysis by Bauer was reprinted by Palache (1935). Preliminary analyses by the writer confirmed the general ratios of the cations, as did the work of Hill (1981). Mg apparently substitutes for both Mn and Zn.
Loseyite is known from but one find in the Franklin Mine, and the specific site was unrecorded. It occurs with calcite, pyrochroite, sussexite, and chlorophoenicite. Valid specimens are exceedingly rare.
Loseyite was named in honor of a mineral collector, Samuel R. Losey, of Franklin.
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| Copyright © 1995 by Pete J. Dunn |
Website
by Herb Yeates
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This
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