Abstract

Switzerite, previously defined as Mn3(PO4)2·4H2O, is the dehydration product of Mn3(PO4)2·7H2O, which is unstable in air. We have proposed that switzerite be redefined as the heptahydrate, and that the tetrahydrate be renamed metaswitzerite. This proposal has been accepted by the New Mineral Names Commission, IMA.

Averages of six microprobe analyses of metaswitzerite gave MnO, 46.05; FeO, 3.60; P2O5, 32.94 (all weight percent), with trace amounts of Si, Ca, Mg, and Al. The empirical formula of switzerite is (Mn0.93Fe0.07)3(PO4)2·7H2O.

The strongest X-ray powder-diffraction lines in ångströms, with intensities and indices, are 11.12(100)(001), 3.37(90)(123), 6.81(60)(111,110), 5.08(60)(121,120), 8.47(50)(011), 2.137(50)(402). Similar data are reported for synthetic Mn3(PO4)2·6H2O (JCPDS 3-0020); the synthetic phase is probably really the heptahydrate. Refinement of the powder data gives a 8.545(2), b 13.164(3), c 11.878(4) Å, β 110.12(3)°, Z = 4. The space group is P21/a from single-crystal X-ray study.

Switzerite is transparent to translucent, pink in color, with a vitreous to pearly luster. Crystals are thin tabular on {001} and the cleavage is perfect on {001}. Dmeas = 2.535; Dcalc = 2.545. Switzerite is soft and brittle, unstable in air, and alters irreversibly to metaswitzerite in minutes. Optically, it is biaxial (−), 2Vmeas = 70°; 2Vcalc = 66°; α 1.560, β 1.574, γ 1.580, (all ±0.001), Z = b, X⊥ (001).

Switzerite occurs in the lower levels of the Foote Mineral Company spodumene mine near Kings Mountain, North Carolina, in fissures in quartz-alkali feldspar-spodumene pegmatite. It is found only in freshly exposed rock, but metaswitzerite is widespread throughout the quarry.

This content is PDF only. Please click on the PDF icon to access.

First Page Preview

First page PDF preview
You do not currently have access to this article.