Modular structures in sulphides: sphalerite/wurtzite-, pyrite/marcasite-, and pyrrhotite-type minerals
Published:January 01, 1997
Mihály Pósfai, Peter R. Buseck, 1997. "Modular structures in sulphides: sphalerite/wurtzite-, pyrite/marcasite-, and pyrrhotite-type minerals", Modular Aspects of Minerals, Stefano Merlino
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Our understanding of mineral structures profoundly changed in the last twenty-five years. High-resolution transmission electron microscopy (HRTEM) and associated techniques revealed that many mineral specimens have their own “personalities” on the atomic scale. The direct viewing of intergrowths and defects provided insights into the structural and compositional relationships between different minerals and mineral groups (Wenk, 1976; Drits, 1987; Buseck & Veblen, 1988; Buseck, 1992).
While rock-forming silicates and some oxides were extensively studied in this expansive period of mineralogical research, the sulphide minerals received less attention. The last comprehensive reviews of sulphides were published in the late 1970’s and early 1980’s and include an excellent book on the mineral chemistry of sulphides (Vaughan & Craig, 1978), the first volume of the Reviews in Mineralogy series (Ribbe, 1974), and a book on the crystal chemistry, parageneses and systematics of sulphides (Kostov & Minčeva-Stefanova, 1982). Another useful structural classification of sulphides was produced by Zoltai (1974) and sulphide mineral stabilities were reviewed by Barton & Skinner (1979). Although progress has been made since these reviews appeared, much remains to be learned about structural details such as defects and intergrowths at the unit cell-scale, and their relationships to composition in simple sulphide minerals.
In this chapter we describe planar defects and ordering phenomena in three groups of sulphides that have relatively simple structures. We define layer modules from which the basic structures and their polytypes and polymorphs are built. These modules are then used to describe the topologies of defects, either observed or
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Modular Aspects of Minerals
Since the first beginning of the crystal chemical study of the inorganic compounds, a simple modular approach was developed, by looking at the crystal structures as built up through the assembling of simple polyhedral units. This approach was no only useful for a vivid and insightful description of the complex atomic arrangements of natural and synthetic compounds, but, through the use of simple and powerful rules for assembling polyhedral units, it displayed an extraordinary heuristic power, suggesting reliable models for many complex structural assemblages. The polyhedral approach also laid the basis for meaningful classifications which were applied to all the classes of inorganic compounds.