Color Black or brown, varying shades Texture Can be smooth, granular, or banded Hardness Soft to hard, depending on coal type Luster Dull to shiny Density Varies depending on coal type, typically around 1.2-1.5 g/cm�³ Porosity Varies, can be porous Composition Mainly composed of carbon, along with hydrogen, sulfur, oxygen, and trace minerals Moisture Content Can range from a few percent to over 30% Volatile Matter Varies, typically 20-45% Fixed Carbon Varies, typically 40-90% Ash Content Varies, typically 3-30% Heating Value (BTU/lb) Varies depending on coal type, typically 8,000-14,000 BTU/lb Heating Value (MJ/kg) Varies depending on coal type, typically 24-33 MJ/kg Combustion Characteristics Burns to release heat, producing carbon dioxide and other gases