Polished fossil Oncolite slab. ONC115 oldest agate in the world Dimensions at widest points approximately

Dimensions at widest points approximately 160 mm x 100 mm x 45 mm thick

Approximate dimensions at widest points 170 mm  x 75 mm  x 55 mm thick

Dimensions approximately 140 mm x 60 mm x 11 mm thick

Weighs 654 grams

Polished fossil Oncolite slab. ONC115 oldest agate in the world Dimensions at widest points approximatelyONC115. 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. 170 mm x 70 mm x 7. 5 mm thick. Weighs 211 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