According to Professor Google, this is Geyserite, a form of opaline silica found around geysers and hot springs. In this case, it was at the base of the Pohutu Geyser in Rotorua New Zealand.
Taken during a 3 week drive around the North Island of New Zealand in late 2019
Ah, brings me back to our holiday to NZ in the nineties. I can still remember that smell. We loved Rotorua. I seem to remember dragging hubby away from the fishing there to go and see some of the other areas of your beautiful country! He'd have stayed the whole 3 weeks there if he'd got away with it!
Thanks for you visit and nice comment. Much appreciated.