IRONSTONE CONCRETIONS - Sahara Desert, Morocco

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IRONSTONE CONCRETION

Sahara Desert, Morocco

In unconsolidated sedimentary rocks iron is often dissolved in the groundwater and can be redeposited as hard, insoluble layers of iron oxide. Round or angular concretions are sometimes formed, consisting of concentric layers of iron minerals such as limonite and goethite.

In this specimen there are two concretions joined together, the deposition of iron oxixe having been controlled by joints in the original rock. The layers of varying hardness have subsequently been picked out by erosion. Sedimentary structures like this are known as boxwork.

A curious item. One for the collector of unusual works of nature!

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Size: 14 x 4.5 x 4.5 centimetres
Weight: 541 grams