Posted by Joe Raine at 02/12/2021 12:15:16
If you don’t know the story of Bethan’s rock, where have you been?! In 2019, after going round the museum and finding out what they do, a young girl named Bethan decided to give us her greatest treasure, her favourite rock. She wanted it to be on show so that other people could enjoy it as much as she did, and it’s taken pride of place on the second floor of the museum ever since. In honour of it recently becoming a social media sensation we’ve decided to feature something else geological from the museum’s collection.
By collecting unusual rocks Bethan was following the footsteps of many great natural scientists, geologists, and mineralogists, including the formidable figure who gave his name to this odd-looking rock…
This strange rock is a sample of the mineral Goethite, one of the main components of rust and bog iron ore and is often formed when other iron-rich minerals start to weather. Goethite can appear in many forms, but our sample is botryoidal, meaning it is globular and looks a bit like a bunch of grapes. It was first officially recorded in 1806 at Hollertszug Mine in Germany but had been used by humans since prehistory, especially ground up as a pigment or in dyes. Samples taken from some of the cave art at Lascaux suggest they were painted with Goethite pigment.
Johann Georg Lenz gave the mineral its name and if it sounds familiar it’s for good reason! The mineral is named after German literary legend Johann Wolfgang von Goethe, the author of Faust. In between writing many famous plays, books and poems Goethe was an accomplished scientist across a range of fields. He studied everything from colour theory to the structure of animal bones but was particularly fascinated by geology and minerology. He is said to have had the largest private collection of geology in Europe at the time of his death, owning about 17,800 rock samples.
We think our example may have come from Canada but Goethite can be found across the world (and even in craters on Mars!) but can look very different from our reddish botryoidal lump.
If you want to find out more, have spotted a strange rock you’d like to identify or just see some more amazing pictures of minerals, gems and rocks then check out https://www.mindat.org/