The crystal chemistry of staurolite
| dc.contributor.author | Griffen, Dana T. | en |
| dc.contributor.department | Geological Sciences | en |
| dc.date.accessioned | 2016-02-01T14:45:02Z | en |
| dc.date.available | 2016-02-01T14:45:02Z | en |
| dc.date.issued | 1972 | en |
| dc.description.abstract | Microprobe analyses of 20 staurolites from many localities indicate that the range of composition of natural ferroan specimens is Fe<sub>2.95-3.44</sub> Al<sub>17.07-17.60</sub>Mg<sub>0.38-1.13</sub>Ti<sub>0.09-0.14</sub>Zn<sub>0-0.17</sub>Mn<sub>0-0.09</sub>Cr<sub>0-0.02</sub>V<sub>≤.01</sub>.Co<sub>≤.004</sub> Si<sub>7.64-7.91</sub>O<sub>44</sub> OH<sub>~4</sub>. Our observations, together with chemical analyses and other experimental evidence from the literature, are sufficient to conclude that the staurolite unit cell contains ~4 H⁺ in agreement with the structural formula of Smith (1968): (7 octahedral sites, principally Al)<sub>~18</sub> (1 tetrahedral site, principally Fe)<sub>≤</sub>₄ (1 tetrahedral site, principally Si)₈O₄₈H<sub>≤</sub>₄ Assuming that Si and a small amount of Al fill the Si<sup>IV</sup> site, we have used the method of principal component analysis to deduce that the primary substitution in the A1<sup>VI</sup> sites is Al ⇄ (Fe+Mg+Ti) and that in the Fe<sup>IV</sup> sites is Fe ⇄ (Zn+Al). Secondary substituents in the AI<sup>IV</sup>sites are M and Zn, and it is likely that small amounts of and Ti are present in the Fe<sup>IV</sup> site. The generally accepted view that Mg is the primary substituent for Fe in the Fe<sup>IV</sup> site is not supported Lattice parameters determined by powder methods on 15 analyzed staurolites show the following ranges: a= 7.865 - 7.879Å; b = 16.600 - 16,633Å; c = 5.656 - 5.664Å; β = 90.0°. There are positive correlations of b and c with Fe content, while a is nearly independent of composition. These relationships are explained on the basis of the crystal structure and site occupancies. Natural specimens have uniformly shorter a cell edges {by ~0.015Å) than synthetic Fe-Mg staurolites. Improved curves showing the relationship of 2V and refractive indices to Fe-content have been established. | en |
| dc.description.degree | Master of Science | en |
| dc.format.extent | v, 34 leaves | en |
| dc.format.mimetype | application/pdf | en |
| dc.identifier.uri | http://hdl.handle.net/10919/64605 | en |
| dc.language.iso | en | en |
| dc.publisher | Virginia Polytechnic Institute and State University | en |
| dc.relation.isformatof | OCLC# 34065995 | en |
| dc.rights | In Copyright | en |
| dc.rights.uri | http://rightsstatements.org/vocab/InC/1.0/ | en |
| dc.subject.lcc | LD5655.V855 1972.G75 | en |
| dc.title | The crystal chemistry of staurolite | en |
| dc.type | Thesis | en |
| dc.type.dcmitype | Text | en |
| thesis.degree.discipline | Geological Sciences | en |
| thesis.degree.grantor | Virginia Polytechnic Institute and State University | en |
| thesis.degree.level | masters | en |
| thesis.degree.name | Master of Science | en |
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