Panethite

PanethiteThe mineral panethite (Na,Ca)₂(Mg,Fe)₂(PO₄)₂ is a rare mineral that was only found in one meteorite on Earth. It was originally found in Dayton meteorite in Ohio. It is classified as H-M Symbol (2/m) with space group of P 2₁/n. Its amber in color and it was named in the honor of Friedrich Adolf Paneth, a German chemist who made many contributions toward the discovery of the origin of the universe, and especially studies of meteorites.

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Introduction

The mineral panethite (Na,Ca)₂(Mg,Fe)₂(PO₄)₂ is a rare mineral that was only found in one meteorite on Earth. It was originally found in Dayton meteorite in Ohio. It is classified as H-M Symbol (2/m) with space group of P 2₁/n. Its amber in color and it was named in the honor of Friedrich Adolf Paneth, a German chemist who made many contributions toward the discovery of the origin of the universe, and especially studies of meteorites.

Composition

By using Electron microprobe analyses, based on 8 atoms of Oxygen, the calculated formula for panethite was found to be (Na_1.44 K_0.06 Mg_1.75 Ca_0.29 Fe_0.22 Mn_0.07 P_1.97 O_8.00). Within analytical error of almost 2% in the amount analyzed was: (Na_1.42 Ca_0.28 K_0.06)_1.76 (Mg_1.70 Fe_0.21 Mn_0.07)_1.98 (PO₄)₂ (Fuchs, 1713).

Structure

Using X-ray Powder, the Cell parameters and the space group were determined. The strongest lines of the X-ray were 5.10(6), 3.236(5), 3.007(10), 2.749, 2.710(7) (American Mineralogist, 509). But the error of the cell lengths were relatively high due to twinning and some disorder in the grains examined. Panethite has a monoclinic crystal system with a0=10.18 +-0.01Å, b0=14.90 +-0.02Å, c0=25.87+-0.03Å & β =91.1˚, and its space group P2₁/n. Within the error that accompanied the microprobe analysis, the X-ray density was found to be 2.99g/ml. Both brianite and panethite were clear and transparent with no crystal faces; and both don’t present any discernible cleavage. Panethite is a Biaxial negative, pale amber in its color and the estimated 2V was approximated to be 51˚. The refractive indices was found by using sodium light, and it was found to has α=1.567, β=1.576, γ = 1.579 all +-0.001 (Fuchs, 1716). Even thought panethite lacks the lamellar structure that brianite shows, panethite shows simple twinning. The higher refractive indices along with the lamellae structure of brianite help us to distinguish these two minerals apart under the microscope. One of the problems was the amount given to study the mineral was little in order to conserve the mineral as much as possible. The hardness of panethite was inconclusive and tested in the same method of brianite. Using sink or float method, the specific gravity of Panethite was between 2.90 to 3.0 g/ml. Both minerals were insoluble in water. Another fact is that panethite and brianite are the most known minerals to have the greatest amount of sodium content in meteorites (Fuchs, 1716). Panethite is named after the director of Max Plancks Institute, Mainz, Germany, Friedrich Adolf Paneth (1887-1958) who made a lot of important contributions in the study of meteorites. As the name Panethite was approved before publication as a new mineral by the IMA (International Mineralogical Association) (American mineralogist, 509).

References

• Fuchs, Louis H.(1967) On the occurrence of Brianite and Panethite, two new phosphate minerals from the Dayton meteorite. Geochimica et Cosmochimica Acta, 31, 1711-1719.
• Fuchs, Louis H. (1968) Panethite. American Mineralogist, 53, 509