Polished fossil Oncolite slab. ONC117 chrysoprase Dimensions approximately 130 mm x

Dimensions approximately 130 mm x 100 mm x 50 mm thick

Dimensions at widest points approximately 105 mm x 70 mm x 9

Dimensions at widest points approximately 105 mm  x 90 mm wide x 9 mm thick

TI284   Tiger Iron slab

Polished fossil Oncolite slab. ONC117 chrysoprase Dimensions approximately 130 mm xONC117. 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. 160 mm x 80 mm x 8. 5 mm thick. Weighs 217 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