Earth and Planetary Sciences ETDs

Publication Date

5-19-1970

Abstract

The potassium ferric sulfate minerals, yavapaiite [KFe(so ) J and goldichite [KFe(so4) •4H2oJ were studied 42 2 using x-ray diffraction methods, and the results correlated with the mineral krausite [KFe(so4)2 ·H20J .

Yavapaiite crystallizes in space group C2/m with two formula weights in a unit cell of dimensions a= 8 .152A, b = 5, 153A, c = 7,877A and S = 911.70°. Goldichite , in space group P2 /c, contains four formula weights in a unit cell with a= 10 . 387A, b = 10.486A, c = 9.086A and 6 = 101.67°.

The structures were solved by three-dimensional Patterson syntheses as well as by application of the symbolic addition procedure for phase determination . Both yavapaiite and goldichite were refined by the full-matrix least-squares method to final residuals of 3.2% and 3.3% respectively.

In yavapaiite, ferric sulfate sheets of composition n[Fe(so ) ]-are linked to paral!el sheets of potassium ions located on the 002 plane. This arrangement accounts for the perfect {001} cleavage of yavapaiite . Coordination polyhedra of iron and sulfur are distorted. The average Fe-0 octahedral and S-0 tetrahedral separations are 1.988A and 1.472A respectively. Potassium with 10 nearest neighbors forms a trigonal antiprism bisected by a square plane; the average K-O separation is 2.958A.

In goldichite, the hydrated ferric sulfate sheets of composition n[Fe(so4)2·2H 0J-are linked to zig-zag sheets of potassium ions and water molecules along [001]. This spatial arrangement accounts for the excellent {100} cleavage of goldichite. In the distorted polyhedral groups, the average Fe-0 octahedral and S(l)-0 and S(2)-0 tetrahedral separations are 2.005A, 1.477A and 1.469A respectively. The average K-O(sulfate) and K-O(water) distances are 2.899A and 3.096A respectively.

Compositional. physical and structural comparisons are presented for yavapaiite, krausite and goldichite.

Details of the observed octahedral distortions were explained by the extended electrostatic valence rule . A plausible hydrogen bonding scheme was determined for krausite and goldichlte; the average H-----O(acceptor) distance in krausite is 2.0A

Degree Name

Earth and Planetary Sciences

Level of Degree

Doctoral

Department Name

Department of Earth and Planetary Sciences

First Committee Member (Chair)

Abraham Rosenzweig

Second Committee Member

J. Paul Fitzsimmons

Third Committee Member

Wolfgang Eugene Elston

Fourth Committee Member

Albert Masakiyo Kudo

Language

English

Document Type

Dissertation

Comments

Sandia Laboratories financial assistance

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