Polished Green Opal slab GRN90 prehnite Dimensions at widest point approximately

Dimensions at widest point approximately 130 mm x 110 mm x 8 mm

Dimensions at widest points approximately 95 mm x 95 mm x 75 mm thick

Oldest agates on Earth

From near Port Hedland in the Pilbara region of  Western Australia

120 mm x 120 mm x 9

Polished Green Opal slab GRN90 prehnite Dimensions at widest point approximatelyGRN90 Green Opal & Magnesite slab, cut and polished on one side . Dimensions at widest points approximately 200 mm x 100 mm x 16 mm thick Weighs 442 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.