Polished fossil Oncolite. ONC111 outback jasper 55 mm x 50 mm

55 mm x 50 mm  x 17 mm

60 mm x 25 mm  x 18 mm

Dimensions at widest points approximately 80 mm x 50 mm x 28 mm thick

natural rough back and a polished face

Dimensions at widest points approximately 170 mm x 150 mm

Polished fossil Oncolite. ONC111 outback jasper 55 mm x 50 mmONC111. Fossil Oncolite polished slab. From the Miocene "Trealla Limestone" north of Carnarvon, Western Australia . Age is approx. 15 million years. Dimensions at widest points approx. 140 mm x 100 mm x 6. 5 mm thick. Weighs 204 grams. Oncolite is a limestone composed largely of oncoidsrounded, 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