Polished Green Opal slab GRN87 slab cut and polished on one

cut and polished on one side with a natural crystalline rear

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 100 mm x 14 mm thick

Dimensions at widest point approximately 120 mm x 70 mm x 9 mm

The pink and red colouration can be attributed to the presence of finely disseminated iron oxides

Polished Green Opal slab GRN87 slab cut and polished on oneGRN87 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.