Know all about Coal and Obsidian properties here. All properties of rocks are important as they define the type of rock and its application. Coal belongs to Sedimentary Rocks while Obsidian belongs to Igneous Rocks.Texture of Coal is Amorphous, Glassy whereas that of Obsidian is Glassy. Coal appears Veined or Pebbled and Obsidian appears Shiny. The luster of Coal is dull to vitreous to submetallic while that of Obsidian is vitreous. Coal is available in black, brown, dark brown, grey, light to dark grey colors whereas Obsidian is available in black, blue, brown, green, orange, red, tan, yellow colors. The commercial uses of Coal are alumina refineries, electricity generation, liquid fuel, manufacture of soap, solvents, dyes, plastics and fibres, paper industry and that of Obsidian are creating artwork, mirror, used in aquariums.