Classification, petrographic expression, and reflectance of native bitumen

Native bitumen is naturally occurring, solid organic material that originates, with few exceptions, from material expelled by sedimentary organic matter during catagenesis. Note that, in this text, the word bitumen is used to mean "native bitumen" rather than the common meaning of organic matter extracted from rocks with organic solvents. Native bitumens, especially those in developed commercial deposits, are often named after people or places. These names have subsequently been applied to bitumens found in other localities. In other instances, otherwise similar occurrences have been given different names. Accordingly, the names given to native bitumens vary; a glossary is appended. This text reviews nomenclature and criteria used in bitumen classification systems, and also examines the petrographic expression and optical properties of bitumens observed through he reflected light microscope.