Cone-in-cone

color photo of cone-in-cone sample

Cone-in-cone is a peculiar structure consisting of nests of cones, one inside another, standing vertically and arranged either in thin beds or at the edges of large concretions. Some cones are less than an inch in height, and others are as much as 10 inches high. They have a ribbed or scaly appearance. Most cone-in-cone is composed of impure calcium carbonate, but occasionally the structure has been found in gypsum, siderite, and hard coal.

In Kansas cone-in-cone is abundant in the Kiowa Formation of Cretaceous age, where it occurs as beds extending laterally for many feet. When eroded or weathered out, it breaks into small pieces that may easily be mistaken for "chopwood" or petrified wood. Although cone-in-cone may look like fossilized wood, it is an inorganic structure, not the result of fossilization. Good specimens may be found in the banks of the Smoky Hill River in Ellsworth County and around Kanopolis Lake. Cone-in-cone also has been reported from the limestones in Montgomery, Lyon, McPherson, Washington, and other counties.

small drawing of Kansas map with Jewell County highlighted in red

The sample pictured above is from Jewell County, Kansas

Sources

Buchanan, Rex C., Tolsted, Laura L., and Swineford, Ada, 1986, Kansas Rocks and Minerals: Kansas Geological Survey, Educational Series 2, 60 p.

Unless noted otherwise, illustrations by Jennifer Sims, Kansas Geological Survey; photographs by John Charlton, Kansas Geological Survey; text by Liz Brosius, Kansas Geological Survey.

Rocks and Minerals | Next Sample | Previous Sample
Mineral Identification | Mineral Hardness Scale