Bitter Springs is a Precambrian fossil locality in Australia, which preserves microorganisms (bacteria and the like) in silica.[1]Its preservational mode ceased in the late Precambrian with the advent of silicifying organisms.[2]
^Butterfield, Nicholas J. (2003). "Exceptional Fossil Preservation and the Cambrian Explosion". Integrative and Comparative Biology43 (1): 166–177. doi:10.1093/icb/43.1.166. PMID21680421.