Polished fossil Oncolite . ONC118

ONC118. 

Fossil Oncolite rough rock, cut and polished on one side with a natural, weathered back.

Sits well as a display specimen !

From the Miocene "Trealla Limestone" north of Carnarvon, Western Australia .

Age is approx. 15 million years.

 Dimensions at widest points approx.  195 mm x 95 mm x 50 mm thick.

Weighs 1,482 grams.

Oncolite is a limestone composed largely of oncoids—rounded, coated grains that grow as thin layers of lime mud accumulate around a tiny nucleus (such as a sand grain or shell fragment) under microbial influence. Formed in shallow, sunlit waters with gentle movement, oncolites often display attractive concentric or wavy banding and are classic indicators of ancient shoreline and lagoon environments.