Know all about Chalk and Obsidian properties here. All properties of rocks are important as they define the type of rock and its application. Chalk belongs to Sedimentary Rocks while Obsidian belongs to Igneous Rocks.Texture of Chalk is Clastic or Non-Clastic whereas that of Obsidian is Glassy. Chalk appears Soft and Obsidian appears Shiny. The luster of Chalk is dull while that of Obsidian is vitreous. Chalk is available in grey, white, yellow colors whereas Obsidian is available in black, blue, brown, green, orange, red, tan, yellow colors. The commercial uses of Chalk are alumina refineries, creating artwork, drawing on blackboards, gymnasts, athletes and mountain climbers use for grip, in aquifers, paper industry, production of lime, raw material for manufacture of quicklime, slaked lime, soil conditioner, whiting, whiting material in toothpaste, paint and paper and that of Obsidian are creating artwork, mirror, used in aquariums.