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The crystal structure and crystal chemistry of valleriite
| Content Provider | Semantic Scholar |
|---|---|
| Author | Allmann, Rudolf |
| Copyright Year | 2005 |
| Abstract | The crystal structure of valleriite has been determined to consist of alternate interlayering of layers of two kinds: a brucite-like layer of composition [Mg.68A1.32 (OH)2]; and a novel sulfide layer of composition [Fe!.07 CU.93S2]. . -* Permanent address: University of Marburg, 355 Marburg, Germany. 74 HOWARD T. EVANS, JR. and RUDOLF ALLMANN The sulfide layer consists of two sheets of sulfur atoms in close-packed association, with all of the tetrahedral sites occupied at random by Fe and Cu atoms. The structure as a whole requires a large superlattice, but can be defined in terms of two separate sublattices: one rhombohedral with hexagonal axes a = 3.792 ::!::.005 A and c = 34.10 ::!::.05 A, space group R:3m, corresponding to the sulfide layers; and one hexagonal with a = 3.070 ::!:: .006 A and c = 11.37 ::!::. 02A, space group P:3 m 1, corresponding to the hydroxide layers. The structure was refined in terms of the two sub lattices separately using twenty 10l countermeasured data (MoKx) for the sulfide substructure (ZFe.Cu = 0.3083 ::!:: .0002, Zs = 0.3791 ::!::.0003) and twelve 10l data for the hydroxide substructure (ZOH = 0.4704 ::!::.0005, referred to c = 34.10 A). The final reliability index for all reflections including eleven OOl data is R = 0.068. The a axes of the two subcells are in the ratio of 21: 17, hence the overall composition of valleriite is 1.526 [Mg.6sAl.sdOH)2] . [Fe1.07Cu.93S2]{ (21/17)2 = 1.526}. This result is in good agreement with analytical data and accounts well for the unusual properties and occurrence of valleriite. Valleriite belongs to a well established group of minerals which have structures where brucite-like layers bearing a positive charge through extensive substitution of magnesium by aluminum (or iron, etc.) are interleaved by negatively charged layers of another kind. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://rruff.info/doclib/zk/vol127/ZK127_73.pdf |
| Language | English |
| Access Restriction | Open |
| Subject Keyword | Aluminum measurement Brucite Charge (electrical) Crystal structure Hydroxide Ion Iron Magnesium Minerals Optimal substructure Pack unit Reflection (computer graphics) Sulfides Zellweger Syndrome Zero-order hold anatomical layer |
| Content Type | Text |
| Resource Type | Article |
