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