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In the sedimentary rocks of North America there occur also extensive and valuable deposits of semifluid and solid hydrocarbons, such as maltha, asphaltum, albertite, grahamite, uintahite, etc., which have arisen, under the most plausible explanation thus far offered, from the concentration by evaporation of fluid hydrocarbons such as petroleum.

Albertite, a bright, coal-like substance, exceedingly rich in volatile hydrocarbon, occupies fissures in Carboniferous rocks in Nova Scotia, and a similar but less lustrous mineral, termed grahamite, occurs in fissures in rock of the same age, near a rich oil-pool in West Virginia.

This series of substances includes natural or rock-gas, petroleum, maltha or semifluid hydrocarbon, and solid hydrocarbons, such as asphaltum, albertite, grahamite, 339 ozokerite, etc.

Albertite, an asphaltic hydrocarbon compound, a soft black material, obtained in Canada.

In its widest sense it embraces the whole range of these substances, including natural gas, the more or less liquid descriptions of petroleum, and the solid forms of asphalt, albertite, gilsonite or uintahite, elaterite, ozokerite and hatchettite.