Asphalt, or Asphaltum,
the most common variety of bitumen; also called mineral pitch. Asphalt is a compact, glassy, brittle, black or brown mineral, which breaks with a polished fracture, melts easily with a strong pitchy odor when heated, and when pure burns without leaving any ashes. It is found in the earth in many parts of Asia, Europe, and the United States, and in a soft or liquid state on the surface of the Dead Sea, which, from its circumference, is called Asphaltites. It is of organic origin, the asphalt of the great Pitch Lake of Trinidad being derived from bituminous shales, containing vegetable remains in the process of transformation. Asphalt is produced artificially in making coal gas. During the process, much tarry matter is evolved and collected in retorts. If this be distilled, naphtha and other volatile matters escape, and asphalt is left behind.
What is known as asphalt rock is a limestone impregnated with bitumen, found in large quantities in the United States and in Switzerland, France, Alsace, Hanover, Holstein, Sicily, and other parts of Europe, the purest forms taking the names of elaterite, gilsonite, albertite, maltha, brea, etc. In the trade there is wide distinction between these and the sandstones, and limestones impregnated with bitumen, which are known as bituminous or asphaltic limestone, sandstone, etc. The latter are usually shipped without being previously treated or refined, and are used principally in street paving. This class is known as bituminous rock. The production of all kinds of asphalt in the United States is nearly 200,000 tons per annum, valued at over $2,000,000, from California, Utah, Oklahoma, Kentucky, and Texas.
Entry from Everybody's Cyclopedia, 1912.