Polished fossil Oncolite slab. ONC114 beryl CW132 Chinese Writing Stone rough

CW132   Chinese Writing Stone rough rock

DO173  Dendritic Opal slab

Sections consist of a chaotic mixture of dolomite and/or stromatolite fragments set in a matrix of mudstone and/or coarsely crystalline dolomite

One edge slightly unpolished

Chinese Writing Stone is a porphyritic basalt (porphyry) with groups and rosettes of plagioclase feldspar

Polished fossil Oncolite slab. ONC114 beryl CW132 Chinese Writing Stone roughONC114. 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 100 mm x 7. 5 mm thick. Weighs 241 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