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The following types of material are excluded (although they may also be collected by crystallography stamp enthusiasts): Postal stationery, [10] e.g. a postcard depicting a crystallographer with a non-crystallographic stamp affixed; Cinderella, local, private or personal issues, i.e. unofficial stamps; Non-postal stamps, e.g. revenue stamps [11]
The Wyckoff positions are named after Ralph Wyckoff, an American X-ray crystallographer who authored several books in the field.His 1922 book, The Analytical Expression of the Results of the Theory of Space Groups, [3] contained tables with the positional coordinates, both general and special, permitted by the symmetry elements.
The symbol of a space group is defined by combining the uppercase letter describing the lattice type with symbols specifying the symmetry elements. The symmetry elements are ordered the same way as in the symbol of corresponding point group (the group that is obtained if one removes all translational components from the space group).
In crystallography, a crystallographic point group is a three dimensional point group whose symmetry operations are compatible with a three dimensional crystallographic lattice. According to the crystallographic restriction it may only contain one-, two-, three-, four- and sixfold rotations or rotoinversions.
The Pearson symbol, or Pearson notation, is used in crystallography as a means of describing a crystal structure. [1] It was originated by William Burton Pearson and is used extensively in Pearson's handbook of crystallographic data for intermetallic phases. [2] The symbol is made up of two letters followed by a number. For example: Diamond ...
Mineral symbols (text abbreviations) are used to abbreviate mineral groups, subgroups, and species, just as lettered symbols are used for the chemical elements. The first set of commonly used mineral symbols was published in 1983 and covered the common rock-forming minerals using 192 two- or three-lettered symbols. [ 1 ]
It lists the International Tables for Crystallography space group numbers, [2] followed by the crystal class name, its point group in Schoenflies notation, Hermann–Mauguin (international) notation, orbifold notation, and Coxeter notation, type descriptors, mineral examples, and the notation for the space groups.
In Hermann–Mauguin notation, space groups are named by a symbol combining the point group identifier with the uppercase letters describing the lattice type.Translations within the lattice in the form of screw axes and glide planes are also noted, giving a complete crystallographic space group.