CHLOROPHOENICITE

(Mn,Mg)₃Zn₂(AsO₄)(OH,O)₆ 
Monoclinic, C2/m, a = 22.98, b = 3.32, c = 7.32 Å,
b = 106.0^o, Z = 2

	Figure 25-20. Crystal drawings of chlorophoenicite from Franklin; these are two projections (A and B) of one crystal. Drawings are from Palache (1935) who provided crystallographic data.

Chlorophoenicite was first described by Foshag and Gage (1924) and was more completely described by Foshag et al. (1927). Palache (1928a) described a purported clinozoisite from Franklin, which was later shown by Bauer and Berman (1930) to be chlorophoenicite. Palache (1935) and Albanese (1967) summarized the extant data and mentioned some new parageneses, including a new occurrence at Sterling Hill. Dunn (1981c) provided new analytical data for both magnesium-chlorophoenicite and chlorophoenicite. X-ray data were given by the ICDD (#25-1159) and discussed by Bayliss and St. J. Warne (1987).

Crystal structure

The crystal structure was described by Moore (1968c) as having slabs composed of MnO-(O,OH) octahedral pyrochroite fragments, connected by [(As_0.5H_0.5)(O,OH)₃], and [Zn(O,OH)₃] tetrahedral chains; these slabs are parallel to {100}.

Description

	Figure 25-21. Euhedral chlorophoenicite crystal apparently “pierced” by a prismatic willemite crystal from Franklin. Field of view is 0.1 mm in maximum dimension.

Chlorophoenicite occurs in fine crystals (Figures 25-20 and 25-21) which commonly form divergent sprays up to 1 cm. Most clorophoenicite is markedly acicular, elongate on [001], and striated parallel to [001] (Figures 25-22 and 25-24). Stout crystals closely resemble those of epidote-group minerals and are best identified using X-ray methods. The forms present are {001}, {100}, {106}, {102}, {104}, {203}, and {111}.

Chlorophoenicite occurs in a variety of textures, including dense, tight masses of acicular crystals, matted white aggregates, and microcrystalline, chalky, white, pulverent coatings.

Chlorophoenicite can have an alexandrite color-effect: the type material is light grayish green in daylight and pinkish in incandescent light. This color change effect is also seen, in a different sense, in gageite and tephroite. Much chlorophoenite is colorless to white in the aggregate; it is easily stained, and anomalous surface colors may result. The luster is vitreous to pearly to silky; cleavage is perfect on {100}; and the density is 3.53 g/cm³.

Optically, chlorophoenicite is biaxial, negative, with 2V = 83^o, a = 1.682, b = 1.690, g = 1.697, and strong dispersion, r > v. There is no discernible fluorescence in ultraviolet.

Composition

Chlorophoenicite is a manganese magnesium zinc arsenate hydroxide mineral with much solid solution of Mg for Mn. Dunn (1981c) provided numerous analyses of chlorophoenicite, demonstrating major, but not complete, solid solution of Mg towards magnesium-chlorophoenicite. Representative analyses are given in Table 25.

Occurrence and paragenesis

Chlorophoenicite is found associated with a large number of species. The original occurrence was of crystals and reticulated masses associated with tephroite, willemite, leucophoenicite, zincite, and calcite and was found between the 500 and 600 levels at Franklin, in an area in the east limb in which schallerite and hedyphane were also found.

	Figure 25-22. Acicular prismatic crystals of chlorophoenicite from Sterling Hill. Field of view is 0.6 mm in  maximum dimension.		Figure 25-23. White chlorophoenicite crystal clusters on ore from Sterling Hill. Specimen is 9 cm in maximum dimension. Smithsonian Institution, #C6564. Photo by the author.

In general, Franklin chlorophoenicite occurs in small amounts in recrystallized vugs and veins with Mn-silicates, most commonly leucophoenicite, tephroite, or gageite, together with zincite, willemite, and calcite. The co-existence of this Mn-Zn arsenate with other compound Mn-Zn minerals, such as hetaerolite and hodgkinsonite, is very common. Chlorophoenicite was reported with pyrochroite and zincite from the Buckwheat Dump by Albanese (1967).

	Figure 25-24. Acicular randomly-grown crystals of chlorophoenicite from Franklin. Field of view is 0.3 mm in maximum dimension.

At Sterling Hill, as at Franklin, chlorophoenicite is widely distributed, although in minor amounts. Palache (1935) reported radial aggregates associated with barite and calcite on the 900 level. In addition to the hodgkinsonite/hetaerolite association, chlorophoenicite is also associated with many of the basic manganese arsenates described herein, particularly in the central zincite and the outer zincite zones in the east and west limbs. Chalky white material has been found on the 700 and 800 levels, as well as in the north orebody. Chlorophoenicite is likely the most ubiquitous arsenate mineral at both Franklin and Sterling Hill.

Name

Chlorophoenicite was named for the Greek words for the colors green and purple-red in allusion to the color-change in the type material.

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