This image was acquired from
wikimedia. It was marked as Public Domain or CC0 and is free to use. To verify, go to the source and check the information there.
Keywords from Image Description:
The Quarterly journal of the Geological Society of London . PROE BONNEY ON THE HORNBLENDC AND OTHER diameter Sir De la Beche mentions the occasional occurrence of fragments of hornblende schist but as he sometimes permits himself as was at that time inevitable little laxity in the use of the term was anxious to settle point