Meanwhile their Horeke property has been put on the market with an asking price of $999,999. Family members are looking after the park until it is sold.
As well as the boulders the 144ha property includes 70ha of beef pasture and a house.
What makes the boulders unusual is the way they have been fluted, or carved into strange shapes, over millennia. Fluted rocks are normally limestone but at Wairere they are basalt, a much harder volcanic rock.
The Schaads moved to New Zealand in 1983 and bought the overgrown, abandoned farm soon afterwards. They became almost as much of an attraction as the boulders themselves.
Mrs Schaad placed a bed in the park visitor's hut, saying it was for geologists who needed a lie down to recover from the shock of discovering fluted basalt; Mr Schaad liked to tell a story about how they bought the property with no idea of its geological wonders until a goat he was chasing through the bush led him to the top of a rock with an astonishing view over a valley littered with giant boulders.
In 2012 Wairere Boulders was voted number 16 on the AA's 101 Must-dos for Kiwis, making it the highest-ranked Northland attraction and eclipsing even Cape Reinga and the Bay of Islands.
The Schaads described their property as a nature park but it has no official conservation status or protection.
