Polished fossil Oncolite. ONC109 polished noreena 90 mm x 65 mm

90 mm x 65 mm x 9 mm thick

160 mm x 110 mm x 10

255 mm x 105 mm  x 12 mm

SD156 Stromatolitic Dolomite slab

Dimensions at widest points approximately 115 mm x 100  mm x 18 mm thick

Polished fossil Oncolite. ONC109 polished noreena 90 mm x 65 mmONC109. 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. 150 mm x 65 mm x 6. 5 mm thick. Weighs 117 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