Mineral inlays in natural stone slabs: techniques, materials and preservation

Abstract

Italy (first) and Spain (second) are the largest producers of marble in the world, and they share a rich history of quarrying and artworks made from natural stone and coloured stones inlaid in marbles. The present decrease of manufactured marble from Spain and Italy is directly related to the increased imports of high quality manufactured natural stone products from Asian countries. Indian stone products are following classic Florentine patterns coupled with modern uses of resins and heavy machinery. Historic lapidary remains of marbles, rocks and semi-precious stones inlaid in tables displayed in the Prado Museum (Madrid, Spain) have been analysed by X-ray diffraction and microscopy using optical lens with guide lights (in situ samples), polarising and scanning-EDAX microscopes. The Florentine table studied has approximately 8000 pieces; however, they belong to a small number of mineralogical species such as quartz, perthite–feldspar, olivine, garnet, sodalite, haüyne, nosean, pyrite, beryl, chrocidolite, chrysotile, malachite, variscite, etc. The classic stone-cutting techniques were analysed through the study of the historic Gasco hydraulic sawmill, which is well preserved and composed of a dam, canal, waterwheel, well, saw room, external workshops and refuse dump (containing the remains of cut marbles, screws, iron fragments, iron balls, etc.). Decolourisation and phase transition tests of stones were carried out using an original self-simultaneous optical stimulation and X-ray diffraction (SOSXRD) system.