Lumachella, also known as opaline lumachella, is a variety of gray marble containing shells that have retained their iridescent luster. Starting from the 1760s, this stone was used in the German lands for the manufacture of jewelry and snuffboxes. The demand for it was so great and the reserves so limited — the main deposit was in Bleiberg, Carinthia (southern Austria) — that by 1820 they were completely exhausted. Cyprien Prosper Brard (1786–1838) in the book Minéralogie appliquée aux arts, published in 1821, noted that by that time, only very small plates of this stone were available to jewelers, and they were extremely expensive. He also pointed out that lumachella had always been too valuable to trust its processing to marble masters: it was processed and polished by the jewelers themselves or by gem cutters.

minimize...