pyrolytic carbon (graphite) approx 5cm square with slightly visible cleavage Source: English Wikipedia, original upload 9 August 2005 by Splarka English
described at URL: https://www.flickr.com/photos/yellowcloud/4648369634/ operator: Flickr URL: https://live.staticflickr.com/4046/4648369634_cbe250c2ab_o.jpg