Concretions are compact, rounded masses of minerals that form within sedimentary rocks. They typically form when minerals precipitate around a nucleus, which can be an organic particle, a fossil, a mineral fragment, or even a void within the rock. Over time, minerals from the surrounding sediment or groundwater accumulate and solidify around this nucleus, forming a solid mass that is often distinct from the host rock.

Concretions can vary greatly in size, ranging from just a few millimeters to several meters in diameter. They can also vary in composition, with the most common minerals involved in their formation being calcite, siderite, pyrite, and silica. The type of mineral that forms a concretion depends on the chemical conditions of the surrounding environment.

Some distinctive features of concretions include:

Concretions can sometimes be mistaken for fossils, meteorites, or other unusual geological formations due to their distinct shapes and compositions. However, they are an important geological phenomenon in their own right, offering valuable insights into the processes that shape sedimentary rocks and the history of the environments in which they form.

Very few of the odd concretions are the same.  The round ones are very close.


 Always be aware of where you are and ask permission to collect.

 Come to the rock shop for more information and to see many fine specimens.