GIANT SANDSTONE CONCRETIONS



Sandstone concretions grow in sedimentary rocks.  As acidic rain or groundwater seeps through the strata it dissolves minerals such as calcite or iron carbonate which is slowly redeposited around some foreign object such as a fossil bone or shell fragment. Concretions are simply sandstone grains cemented together by solidified minerals.

They may form over millions of years into any size or shape but usually as a sphere. They will continue to grow until the ground dries up or erosion exposes them where we may find them.

I found these five foot sandstone concretions in a 
hidden location on the Hopi Reservation in Arizona.

Besides these rolling around several others are still buried.

One is shattered exposing layers like an onion.

Unfortunately the site was a party ground for the locals. There was glass and trash scattered about and shots had been fired at the one on the pedestal. Look close and you can see the pockmarks on it. Too bad!

These concretions in Arizona are on the high desert and 5 to 6 feet in diameter. I did a net search and found some other notable locations where they are found.

Bowling Ball Beach in Northern California.

One at an unknown location in Montana.

Theodore Roosevelt National Park, North Dakota

Moeraki Boulders in New Zealand

Moeraki Boulder ten feet in diameter.