Darwin wrote: “Basaltic amygdaloidal with crystals of augite, forming dykes near landing place.”
This amygdaloidal monchiquite dyke rock contains euhedral phenocrysts of hornblende and pyroxene. The microcrystalline groundmass is dominated by small needles of hornblende. Amygdales are infilled with zeolite species, including chabazite.
This collection was a collaboration between The Open University and the Sedgwick Museum, created in 2009 to celebrate the bicentennial of the birth of Charles Darwin.
The Sedgwick Museum opened a new gallery, 'Darwin the Geologist', and created a museum-based virtual microscope to showcase rocks he collected during the Voyage of the Beagle. We enjoy this collection because Darwin did not always pick up a representative sample from the islands he visited; it's often the unusual rocks that caught his eye. Just explore the collection and you'll see what we mean. For those who have the opportunity, a visit to the museum is strongly recommended.