Polished Green Opal slab GRN87 slab Dimensions approximately 90 mm x

Dimensions approximately 90 mm x 80 mm x 75 mm thick

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

OG175   Polished orbicular granite with natural rough back

PA263  Pilbara Agate rough rock

Polished Green Opal slab GRN87 slab Dimensions approximately 90 mm xGRN87 Green Opal & Magnesite slab, cut and polished on one side . Dimensions at widest points approximately 110 mm x 80 mm x 10 mm thick Weighs 171 grams Green Opal occurs at a location south of Kalgoorlie in the Eastern Goldfields of Western Australia. The green colouration is caused by traces of nickel and or chromium. Sometimes it exhibits striking contrasting veins of magnesite.