MOOREITE

Mg₉Zn₄Mn₂(SO₄)₂(OH)₂₆.8H₂O
Monoclinic, P2₁/a, a = 11.147, b = 20.350, c = 8.202 Å,
b = 92.69^o, Z = 2

	Figure 24-14. Crystal drawing of mooreite from Sterling Hill. Drawing is from Palache (1935) who provided crystallographic data.

Mooreite was first described from Sterling Hill by Bauer and Berman (1929b, 1929d) and was restudied by Prewitt-Hopkins (1949).

It was again restudied by Finney (1969) who corrected Prewitt-Hopkins’s data and provided a correct unit-cell. Mooreite was subsequently redefined by Hill (1979), who provided X-ray data and the formula above. Mooreite has not been reported from Franklin.

Crystal structure

Hill (1980) provided a description of the crystal structure. The basic units of the structure are brucite-like sheets of edge-sharing Mg octahedra oriented parallel to (010). Vacant octahedral sites in these sheets share upper and lower faces with tetrahedral [Zn(OH)₄] groups. Octahedra of [Mn(OH₂(H₂O)₄] are also sandwiched between the sheets. Sulfate groups are held in the interlayer region.

Description

Mooreite crystals are tabular on [010] and generally platy in habit (Bauer and Berman, 1929b; Palache, 1935) (Figure 24-14) and arranged in subparallel growth; some clusters are curved in part. The color is light yellowish brown, but very small crystals appear colorless. Cleavage is perfect on {010}, and the luster is vitreous to pearly. The density is 2.47 g/cm³. Optically, mooreite is biaxial, negative, 2V = 50^o, with a = 1.533, b = 1.545, and g = 1.547; dispersion is r > v, perceptible. There is no discernible fluorescence in ultraviolet.

Composition

Mooreite is a magnesium manganese zinc sulfate hydroxide hydrate mineral. Selected analyses are presented in Table 23 and show the composition to be fairly constant. Numerous unpublished analyses by the writer indicate that Fe and Ca are absent or present only as traces, that Zn and S are nearly constant, and that there is some mutual substitution between Mn and Mg. The extremes of Mn/Mg solid solution are indicated by the two partial analyses in Table 23; the SO₃ values in the writer’s three analyses are a bit low. Hill (1979) reported thermal and infrared data.

Occurrence and paragenesis

Mooreite is known only from Sterling Hill. It occurs intimately associated with pyrochroite, torreyite, fluoborite, rhodochrosite, and zincite in cavities and in vein occurrences in normal ore. Mooreite in this assemblage occurs in glassy white to colorless crystals (Figure 24-15), in platy masses (Figure 24-16), and also lining cavities in pyrochroite. Available specimens suggest that there are a number of additional occurrences for mooreite at Sterling Hill.

	Figure 24-15. Tabular, pinacoidal crystal of mooreite from Sterling Hill. Field of view is 1.4 mm in maximum dimension.		Figure 24-16. Platy massive mooreite on ore from Sterling Hill. Specimen is 13 cm in maximum dimension. Smithsonian Institution, #164133. Photo by the author.

Broad, flat plates of mooreite, light brown and up to 10 cm, are known, and mooreite has been found with pyrochroite in the north orebody near the 2250 level. The old name delta-mooreite was applied to what is now known as torreyite.

Name

Mooreite was named for Dr. Gideon Moore, chemist of the precursor companies of the second New Jersey Zinc Company and describer of several new Sterling Hill minerals, including chalcophanite and hetaerolite.

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