Know all about Greywacke and Coal properties here. All properties of rocks are important as they define the type of rock and its application. Greywacke and Coal belong to Sedimentary Rocks.Texture of Greywacke is Clastic whereas that of Coal is Amorphous, Glassy. Greywacke appears Dull and Coal appears Veined or Pebbled. The luster of Greywacke is dull while that of Coal is dull to vitreous to submetallic. Greywacke and Coal are 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 Greywacke are as armour rock for sea walls, petroleum reservoirs, sea defence, tombstones and that of Coal are alumina refineries, electricity generation, liquid fuel, manufacture of soap, solvents, dyes, plastics and fibres, paper industry.