Cupped NY Stone

[Ron Kelley]

Can someone tell me what these are? They are from Long Island New York. I'm guessing that they have a high iron content.

[painshill]

Hi Ron
Those are the broken shells of iron-rich sandstone concretions of the kind sometimes referred to as “Indian paint pots” (although they’re completely natural). For Long Island, they are from Cretaceous sediments and normally clay-filled. Iron oxides and hydroxides from ground water have precipitated around a lump of clay in a layer of sand, cementing the sand as a hard crust around the soft clay. When they break, the soft clay washes out and leaves the hard shell, which may be red-brown or red-purple hematite, dark brown or yellow-brown goethite and/or limonite.
When the continental glaciers melted and the sea-level rose, almost all of the Cretaceous deposits around Long Island were submerged under the ocean but there are a few places where the pre-glacial sediments are exposed above sea level… notably at Garvies Point. These concretions can be found abundantly along the beach there as hollow hemispheres and partial fragments which have eroded out of the sediments and been broken open by wave action. The beach is also rich in irregular rounded lumps of oxidised iron pyrite.

[Ron Kelley]

Thanks Roger, I have seen these for sale many times. My one surprise is that the name "Indian Paint Pot" is a common name for this geofact. Oh well the "Indian Paint Brush" wasn't used to paint with either.

[Hoss]

The Indian Pipe was not used to smoke either