A Jurassic Silicified Coral described in Sowerby 1809

Replacement of fossils by silica can preserve fine-scale features (e.g. Roniewicz 1970, and see Butts 2014). Perhaps the most famous instance is that of the Permian Vidrio Formation in the Glass Mountains of West Texas (e.g. King 1930). Sowerby (1809, p. 181) provided an early illustration of another such case from the Jurassic of England (his TAB. CCXCI), shown below. Sowerby named the specimen ' S I L E X Quartzum coralliformis. Coralliform Flint. Div. 2. Imitative. ' and wrote: ' This is one of the most beautiful, and perhaps local, of the Flint Coral formations, and is found in tolerable abundance in a field near Tidsbury, Wiltshire , in pieces, sometimes as large as a quartern loaf. Some specimens show the remaining form of a real Coral most perfectly having at the same time little globular infiltrations, as if in the act of filling the spaces of the Coral with a whitish calcedony or cachalong-like substance, which more solidly pervades the Flint in other parts ; and a...