Know all about Obsidian and Gritstone properties here. All properties of rocks are important as they define the type of rock and its application. Obsidian belongs to Igneous Rocks while Gritstone belongs to Sedimentary Rocks.Texture of Obsidian is Glassy whereas that of Gritstone is Earthy. Obsidian appears Shiny and Gritstone appears Layered and Foliated. The luster of Obsidian is vitreous while that of Gritstone is dull. Obsidian is available in black, blue, brown, green, orange, red, tan, yellow colors whereas Gritstone is available in beige, black, brown, colourless, cream, dark brown, green, grey, light green, light to dark grey, pink, red, white, yellow colors. The commercial uses of Obsidian are creating artwork, mirror, used in aquariums and that of Gritstone are an oil and gas reservoir, as a feed additive for livestock, gemstone, metallurgical flux, production of lime, soil conditioner, source of magnesia (mgo), tombstones.