BURKE J.G. (1986) Cosmic Debris, Meteorites in History, Chapter 4, p. 121: Chladnite:
Again, it was an observation by Charles U. Shepard that paved the way toward the identification of the pyroxenes. In 1846 he described a mineral which, he wrote, "is a ter-silicate of magnesia...[and] forms more than two-thirds of the Bishopville stone". He named the mineral chladnite "in honor of Chladni, the scientific founder of this department of knowledge." Two years later Shepard reported his analytical results: 70 percent silicic acid, 28 percent magnesia, and 1 percent soda, so that the ratio of oxygen in the magnesia to that in the silica was 1 to 3. In 1851 Sartorius von Waltershausen analyzed a fragment of the Bishopville meteorite and arrived at about the same results, but also found 1.5 percent alumina. Though making errors in his calculations, Sartorius did produce the correct formula - MgO,SiO2; however, he postulated that chladnite was a kind of wollastonite, in which magnesia substituted for lime. The issue was confused further in 1861, when Rammelsberg found by analysis almost 3 percent alumina, 35 percent magnesia, and only 57.5 percent silicic acid. Doubting the existence of a definite mineral, Rammelsberg did not attempt to devise a chemical formula. Meanwhile, Shepard in 1854 described the Tucson iron meteorite and speculated that certain inclusions were chladnite. J. Lawrence Smith immediately corrected him, pointing out that the inclusions were actually olivine, and added a note that he suspected "chladnite is likely to prove a pyroxene". At about the same time, in 1855, Gustav A. Kenngott, professor of mineralogy at Zurich, published a memoir giving details of the minerals of what he termed the "augite group" of the pyroxenes. One member of the group was enstatite, which, Kenngott wrote, was a bisilicate of magnesia, was "augitic in crystallization," and had the formula 3MgO,2SiO3. In 1861, when Kenngott saw Rammelsberg's analysis of chladnite, he insisted that the mineral was identical with enstatite. Smith then made two analyses of the Bishopville meteorite and reported in 1864 that chladnite consisted of 60 percent silica and nearly 40 percent magnesia. He agreed with Kenngott that the mineral was the magnesian pyroxene, enstatite, and accepted Kenngott's formula, in which the oxygen content of the magnesia to that of the silica was 1 to 2. Both Rammelsberg and Maskelyne acted to clarify the formula of enstatite, and through his work on the Breitenbach, Bustee, and Manegaon meteorites, Maskelyne recognized the existence of solid-solution series that included enstatite and bronzite. By the 1870s mineralogists began to report regularly these constituents in meteorites. ______________________________________________ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
