Residuals of a game of marbles from the gods? Calcified alien eggs? Or common geographical formation?

Driving down south from Oamaru towards Dunedin on National Highway No. 1 the road passes a site of outstanding natural beauty just south of Herbert were ca 12 almost perfectly spherical rocks seem to be randomly strewn around a beautiful bay. Here in the agricultural heartland of New Zealand, with its outstanding long and curvaceous beaches, these boulders with a diameter of up to 1.50m look like they have been left lying around by some otherworldly giants after playing boules on their favourite beach.

Maori legend has it that Kai - Hinaki (food baskets) were washed on the shore after the canoe Arai - Uru was wrecked off the coast while searching for jade.

Scientifically it looks like these are septarian concretions cemented by calcite (and about 1% dolomite). They formed in paleocene mudstones and were then washed out by the water on the beach. There they slowly decay and fall apart.

An encounter with these humongous pebbles is always an experience: Not for the droves of chattering spanish tourists and sulking german visitors, but for the feeling of the sheer playfulness of nature, who obviously had a fun day when shaping this beach.