Polished Marble Bar Chert slab MB113 crystophase Porphyry is a general term

Porphyry is a general term that is used rather loosely for  igneous rocks which contain relatively large isolated crystals set in a fine-grained groundmass

Dimensions at widest points approximately  120 mm x 70 mm x 7 mm thick

OJ204  A slab

Dimensions at widest points approximately 60 mm x 50 mm x 38 mm thick

Dimensions at widest points approximately 190 mm x 100 mm x 75 mm thick

Polished Marble Bar Chert slab MB113 crystophase Porphyry is a general termMB113 Marble Bar Chert slab polished on one side . Dimensions at widest points approximately 100 mm x 80 mm x 8. 5 mm thick. Weighs 156 grams. Marble Bar chert is a finely banded, iron rich silica rock from the Marble Bar Chert Member (Warrawoona Group) of Western Australia. Formed in shallow Archean seas, it dates to the Paleoarchean (~3. 46 billion years old), making it one of the Earths oldest well preserved sedimentary rocks. From near the town of