Know all about Obsidian and Siltstone properties here. All properties of rocks are important as they define the type of rock and its application. Obsidian belongs to Igneous Rocks while Siltstone belongs to Sedimentary Rocks.Texture of Obsidian is Glassy whereas that of Siltstone is Clastic. Obsidian appears Shiny and Siltstone appears Rough. The luster of Obsidian is vitreous while that of Siltstone is dull. Obsidian is available in black, blue, brown, green, orange, red, tan, yellow colors whereas Siltstone is available in brown, red, reddish brown colors. The commercial uses of Obsidian are creating artwork, mirror, used in aquariums and that of Siltstone are raw material for the manufacture of mortar, soil conditioner.