page_title: Coal ball
section_title: Distribution
hierarchical_section_title: Coal ball / Distribution
caption_attribution_description: Photo of a large coal ball from southern Illinois now in National Museum Cardiff
context_page_description: A coal ball is a type of concretion, varying in shape from an imperfect sphere to a flat-lying, irregular slab. Coal balls were formed in Carboniferous Period swamps and mires, when peat was prevented from being turned into coal by the high amount of calcite surrounding the peat; the calcite caused it to be turned into stone instead. As such, despite not actually being made of coal, the coal ball owes its name to its similar origins as well as its similar shape with actual coal.
  Coal balls often preserve a remarkable record of the microscopic tissue structure of Carboniferous swamp and mire plants, which would otherwise have been completely destroyed. Their unique preservation of Carboniferous plants makes them valuable to scientists, who cut and peel the coal balls to research the geological past.
  In 1855, two English scientists, Joseph Dalton Hooker and Edward William Binney, made the first scientific description of coal balls in England, and the initial research on coal balls was carried out in Europe. North American coal balls were discovered and identified in 1922. Coal balls have since been found in other countries, leading to the discovery of hundreds of species and genera.
context_section_description: Coal balls were first found in England, and later in other parts of the world, including Australia, Belgium, the Netherlands, the former Czechoslovakia, Germany, Ukraine, China, and Spain. They were also encountered in North America, where they are geographically widespread compared to Europe; in the United States, coal balls have been found from Kansas to the Illinois Basin to the Appalachian region.
  The oldest coal balls were from the early end of the Namurian stage (326 to 313 mya) and discovered in Germany and former Czechoslovakia, but their ages generally range from the Permian (299 to 251 mya) to the Upper Carboniferous. Some coal balls from the US vary in age from the later end of the Westphalian (roughly 313 to 304 mya) to the later Stephanian (roughly 304 to 299 mya). European coal balls are generally from the early end of the Westphalian Stage.
  In coal seams, coal balls are completely surrounded by coal. They are often found randomly scattered throughout the seam in isolated groups, usually in the upper half of the seam. Their occurrence in coal seams can be either extremely sporadic or regular; many coal seams have been found to contain no coal balls, while others have been found to contain so many coal balls that miners avoid the area entirely.
caption: A coal ball from southern Illinois
exif: {"Image Make": "Canon", "Image Model": "Canon EOS 5D Mark III", "Image Orientation": "Horizontal (normal)", "Image XResolution": "72", "Image YResolution": "72", "Image ResolutionUnit": "Pixels/Inch", "Image DateTime": "2012:07:31 22:52:30", "Image Artist": "Geni", "Image YCbCrPositioning": "Co-sited", "Image Copyright": "CC-BY-SA", "Image ExifOffset": "238", "GPS GPSVersionID": "[2, 3, 0, 0]", "Image GPSInfo": "8808", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "8920", "Thumbnail JPEGInterchangeFormatLength": "8670", "EXIF ExposureTime": "1/60", "EXIF FNumber": "4", "EXIF ExposureProgram": "Program Normal", "EXIF ISOSpeedRatings": "400", "EXIF ExifVersion": "0230", "EXIF DateTimeOriginal": "2012:03:18 21:11:46", "EXIF DateTimeDigitized": "2012:03:18 21:11:46", "EXIF ComponentsConfiguration": "YCbCr", "EXIF ShutterSpeedValue": "6", "EXIF ApertureValue": "4", "EXIF ExposureBiasValue": "0", "EXIF MeteringMode": "Pattern", "EXIF Flash": "Flash fired, compulsory flash mode", "EXIF FocalLength": "45", "EXIF SubSecTime": "00", "EXIF SubSecTimeOriginal": "00", "EXIF SubSecTimeDigitized": "00", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "2480", "EXIF ExifImageLength": "2432", "Interoperability InteroperabilityIndex": "R98", "Interoperability InteroperabilityVersion": "[48, 49, 48, 48]", "EXIF InteroperabilityOffset": "8778", "EXIF FocalPlaneXResolution": "1920000/487", "EXIF FocalPlaneYResolution": "320000/81", "EXIF FocalPlaneResolutionUnit": "2", "EXIF CustomRendered": "Normal", "EXIF ExposureMode": "Auto Exposure", "EXIF WhiteBalance": "Auto", "EXIF SceneCaptureType": "Standard"}