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 . ON THE NORTHERN SLOPES OF CADER IDRI chloric acid residue of dusky grey or colourless matter remains In this some pumiceous particles may be made out but the oolitic grains themselves leave siliceous residue which no longer affects polarized light although the concentric