Magnesiochlorophoenicite



Magnesium-chlorophoenicite (magnesiochlorophoenicite) is a magnesium manganese zinc arsenate hydroxide mineral. The original analysis (Palache, 1935) was of admittedly impure material. Dunn (1981c) re-analysed three purported type specimens; only one had Mg > Mn, together with previously unpublished analyses of three additional specimens subsequently studied. It is noteworthy that in all four extant analyses of magnesium-chlorophoenicite there is a surfeit of zinc; Zn varies from 2.4 to 2.8 Zn per five divalent cations. X-ray powder diffraction indicates that magnesium-chlorophoenicite is isostructural with chlorophoenicite; thus, some Zn must be in octahedral coordination substituting for (Mg,Mn). Magnesium-chlorophoenicite may not be stable as an end-member and may require octahedrally coordinated Mn or excess Zn for structural stability. The maximum Mg content known to date is 1.73 Mg per 5 divalent cations.
Magnesium-chlorophoenicite was first reported from Franklin by Palache (1935); it has not been verified from Sterling Hill, but may occur there, inasmuch as more Mg-bearing arsenates are found there than at Franklin. Magnesium-chlorophoenicite was redefined by Dunn (1981c) who provided much compositional data. Unit-cell data and X-ray powder diffraction data were given by Bayliss and St. J. Warne (1987). Magnesium-chlorophoenicite is isostructural with chlorophoenicite.
Magnesium-chlorophoenicite occurs as radial aggregates of fibrous white or colorless crystals; such sprays are up to 12 mm in diameter and are commonly splayed. The species is easily stained, and crystals may appear brown on the surface. Cleavage is perfect. The density is 3.45 g/cm3. There is no discernible fluorescence in ultraviolet. Three specimens were examined by [Dunn]; on all three magnesium-chlorophoenicite occurs as white, radial sprays of acicular crystals. It is best verified using both quantitative chemical analysis for Mg and Mn and X-ray methods.
The type magnesium-chlorophoenicite occurs as radial, 1 cm aggregates associated with zincite and carbonate minerals and was found on the 750 level at Franklin. Additional specimens seen by [Dunn] appear to be from this assemblage. The most Mg-rich magnesium-chlorophoenicite known consists of willemite/franklinite ore with a partially open vein filled with pink, massive, opaque hodgkinsonite, white barite, and zincite crystals. Interstitial spaces among these minerals are filled with snow-white magnesium-chlorophoenicite in radial sprays of acicular crystals. This assemblage is in turn covered by a second generation of druse barite, calcite, and hodgkinsonite crystals. The extant analyses (Dunn, 1981c), together with numerous X-ray investigations, suggest that magnesium-chlorophoenicite is very rare. (Dunn, 1995)


 Location Found: Franklin (Type Locality), unique to Franklin/Ogdensburg area
     
 
 Year Discovered: 1935
     
 Formula: (Mg,Mn)3Zn2(AsO4)(OH,O)6
 Essential Elements: Arsenic, Hydrogen, Magnesium, Oxygen, Zinc
 All Elements in Formula: Arsenic, Hydrogen, Magnesium, Manganese, Oxygen, Zinc
     
 IMA Status: Approved
     
     
 To find out more about this mineral at minDat's website, follow this link   Magnesiochlorophoenicite

     
 References:
Dunn, Pete J. (1995). Franklin and Sterling Hill New Jersey: the world's most magnificent mineral deposits. Franklin, NJ.: The Franklin-Ogdensburg Mineralogical Society. p.671. 'Magnesium-chlorophoenicite'

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.65


The Picking Table References
 PT Issue and PageDescription / Comment
View IssueV. 30, No, 2 - Fall 1989, pg. 19Research Reports, Haidingerite Magnesium-Chlorophoenicite
View IssueV. 9, No. 1 - February 1968, pg. 15The Exclusive Minerals of Franklin/Ogdensburg, N.J. (as of January 1968) by Frank Z. Edwards - Magnesium Chlorophoenicite (Short Note)
View IssueV. 7, No. 2 - August 1966, pg. 11The Minerals of Sterling Hill 1962-65 by Frank Z. Edwards - Magnesium Chlorophoenicite
     
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