A large sample of glassy carbon with a weight of ca. 570 g, as well as a 1 cm3 graphite cube for comparison. By Alchemist-hp (talk) (www.pse-mendelejew.de) [FAL (http://artlibre.org/licence/lal/en/)], from Wikimedia Commons

https://commons.wikimedia.org/wiki/File:Glassy_carbon_and_a_1cm3_graphite_cube_HP68-79.jpg