Catholic Encyclopedia (1913)/Cosmati Mosaic
A peculiar style of inlaid ornamental mosaic introduced into the decorative art of Europe during the twelfth century, by a marble-worker named Laurentius, a native of Anagni, a small hill-town thirty-seven miles east-south-east of Rome. Laurentius acquired his craft from Greek masters and for a time followed their method of work, but early in his career, freeing himself from Byzantine traditions and influences, he worked along original lines and evolved a new style of decorative mosaic, vigorous in colour and design, which he invariably employed in conjunction with plain or sculptored marble surfaces, making it a decorative accessary to some architectural feature. As a rule he used white or light-coloured marbles for his backgrounds; these he inlaid with squares, parallelograms, and circles of darker marble, porphyry, or serpentine, surrounding them with ribbons of mosaic composed of coloured and gold-glass tesseræ. These harlequinads he separated one from another with marble mouldings, carvings, and flat bands, and further enriched them with mosaic. His earliest recorded work was executed for a church at Fabieri in 1190, and the earliest existing example is to be seen in the church of Ara Coeli at Rome. It consists of an epistle and gospel ambo, a chair, screen, and pavement. In much of his work he was assisted by his son, Jacobus, who was not only a sculptor and mosaic-worker, but also an architect of ability, as witness the architectural alterations carried out by him in the cathedral of Cività Castellana, a foreshadowing of the Renaissance. This was a work in which other members of his family took part, and they were all followers of the craft for four generations. Those attaining eminence in their art are named in the following genealogical epitome: Laurentius (1140-1210); Jacobus (1165-1234); Luca (1221-1240); Jacobus (1213-1293); Deodatus (1225-1294); Johannes (1231-1303). Their noted Cosmatesque mosaics are to be seen in the Roman churches of SS. Alessio e Bonifacio, S. Sabba, S. Cesareo, S. Giovanni a Porta Latina, S. Maria in Cosmedin, S. Balbina, S. Maria sopra Minerva, S. Maria Maggiore, and in the cloister of S. Scholastica at Subiaco, the basilica of St. Magus at Anagni, the duomo of Cività Castellana, and the ruined shrine of St. Edward the Confessor in Westminster Abbey.
DE MONTAULT, Généalogie d'artistes italiens; COLEMAN, Cosmati Mosaicin The Architectural Record (New York, June, 1902), XII; PARKER, The Archæology of Rome (Oxford, 1876), Pt. XI; DE ROSSI, Delle altre famiglie di marmorarii romani (Rome, 1870).