Know all about Siltstone and Tachylite properties here. All properties of rocks are important as they define the type of rock and its application. Siltstone belongs to Sedimentary Rocks while Tachylite belongs to Igneous Rocks.Texture of Siltstone is Clastic whereas that of Tachylite is Vitreous. Siltstone appears Rough and Tachylite appears Glassy. The luster of Siltstone is dull while that of Tachylite is resinous. Siltstone is available in brown, red, reddish brown colors whereas Tachylite is available in black, dark brown colors. The commercial uses of Siltstone are raw material for the manufacture of mortar, soil conditioner and that of Tachylite are cemetery markers, creating artwork.