Byzantine Floor Patterns of Interlocking Twisted Cable Loops

Abstract

The twisted-cable type of patterns is found as Late Roman–Byzantine and early Umayyad floor patterns, with considerable uniformity in texture, colors, and technique. They consist of ‘cables’ which together form circles, circle segments, squares and other visually prominent ornamental elements. Cables mostly form complex closed loops, joined at points of local overlap by interlocking ‘knots’. The loops are the inconspicuous construction elements and several of them participate in each visually prominent segmented circle, square, etc. Majority of these patterns are tetragonal with chiral character, with predominant 2D layer-group symmetry p422. Other symmetries are rare, mostly in circular designs. Most of patterns were dichroically colored using local marbles. The combination of loops and knots generates broad versatility of design and a rich spectrum of extant patterns. The principal artistic heritage of this mosaic style are the Cosmatesque floor patterns of central Italy.

Appendix: Chirality/Enantiomorphism

A motif (object, pattern) which can exist in two forms which are non-superimposable images of one another is chiral. One everyday example is your right and left hands, which are related by reflection on a plane halving your body but not in the hands themselves. Chirality (from χειρος—hand) or enantiomorphism (εναντιος—opposite) [according to the science branch you consult] is important in mineralogy, solid-state science and physics, organic chemistry and especially in biochemistry, which is the world of chiral molecules.

Chiral objects (motifs, patterns) themselves do not contain reflection planes and/or centers of inversion (they lack internal mappings of the type x, y, z → x, − y, z and x, y, z → − x, − y, − z) and their symmetry operations can be described by (a set of) rotation axes of symmetry, e.g., as plane and layer groups p4, and p422, or as the symmetry of an ‘untreated’ natural quartz crystal, which has the point group 32. The two enantiomorphs can be ‘superimposed’ only in your imagination, using a reflection on an imaginary plane placed between them. Definition of the handedness, that is, whether the object is right- or left-handed, is important in physics and (bio)chemistry but may be irrelevant for the relatively scarce examples in the art. Problems arising from enantiomorphism in tile art were illustrated in Makovicky and Ghari (2018).