Rocks and Ores

From Ohio History Central

Rock can be defined as a solid body of one or more kinds of minerals. In a few cases, however, rocks may contain material that is not mineral. An example of this is coal, which sometimes contains bits of organic matter.

Some other characteristics that help to define most rocks are:

  • Naturally formed
  • Nonliving
  • Firm, solid matter
  • A mass that sticks together
  • Makes up part of a planet such as Earth, especially in its outer crust

An ore also is a mixture of one or more minerals. We distinguish ore from rock in that a valuable and/or useful material can be mined or extracted from the ore. This material often is a metal. Iron ore, for example, is mined for its iron content. Mining companies sell the ore to manufacturers who extract the iron and use it in producing iron and steel products. The portion of the ore that is not iron is considered a waste or byproduct. Even though it is considered a waste of the iron process, the byproduct may be useful in some other process.

Not all ores are rocks. This is because some ores are not firm and solid. Oil is a liquid "ore;" natural gas is a gaseous "ore." Workers "mine" both of these "industrial minerals" for economic benefit, and consumers use them in their daily lives.


  • American Geological Institute Dictionary of Geological Terms; Dolphin Books, Garden City, NY; 1962.
  • Coogan, Allan H. Ohio’s Surface Rocks and Sediments; Chapter 3 in Fossils of Ohio, edited by Rodney M. Feldmann; Ohio Geological Survey, Bulletin 70, 1996.
  • Melvin, Ruth W. & Gary D. McKenzie. Guide to the Building Stones of Downtown Columbus [Ohio]: A Walking Tour; Ohio Geological Survey, Guidebook No. 6.
  • Pough, Frederick H. A Field Guide to Rocks and Minerals; Houghton Mifflin, Boston, MA; 1976.
  • Skinner, Brian J. & Stephen C. Porter The Blue Planet: An Introduction to Earth System Science; Wiley, New York; 1995.
  • Sorrell, Charles A. Rocks and Minerals; Golden Press, New York, NY; 1973.
  • Wolfe, Mark E., compiler 1997 Report on Ohio Mineral Industries; Ohio Division of Geological Survey; 1998

See Also