Definition and formation: Partings are laminae or beds of noncoal rock, usually mudstone or claystone, in coal beds. They form from sedimentation during flooding of the peat that ultimately became a coal bed. Some coal beds have many partings, some do not. Some partings are regional extent, but most are local.
Discontinuities and obstacles and potential hazards: Partings are not potential hazards and are not normally considered discontinuities, as they do not commonly form vertical barriers or disruptions in a seam (although they could be considered horizontal discontinuities). Occasionally, however, abrupt thickening of partings or dramatic increases in the number of partings do cause lateral obstacles or discontinuities in coal seams.
Trends: Some seams have widespread partings with uniform thickness at mine scale. The Fire Clay (Hazard No. 4) coal bed in eastern Kentucky has a flint-clay parting across much of the coal field. The Herrin (W. Ky. No. 11) coal bed in western Kentucky has a shale parting (blue band) across much of its extent. Widespread partings are part of mining and easily mitigated by coal processing (coal cleaning, preparation, beneficiation). Local changes in parting thickness and abundance are more problematic. In some mines, small areas of increased partings have been noted in floor rolls (swags). These generally have elongate to slightly sinuous trends that can be projected in advance of mining when first encountered. In a Pond Creek coal mine, a narrow band of interbedded sand and coal was documented along an elongate trend, which was a local discontinuity (Greb and Popp, 1999). In other cases, partings increase in thickness and number in a specific direction. Directional increases in parting thickness or abundance may indicate approaching splits or paleochannel cutouts.
Known Kentucky occurrences: Partings are common in coal beds. Eastern Kentucky coals tend to have greater parting variability than do mined coals of the Carbondale Formation in western Kentucky. Coals in the Tradewater Formation and the Baker (W. Ky. No. 13) coal, Shelburn Formation, in western Kentucky are prone to parting variability. Most of the time, partings are not discontinuities, but increased percentage of parting material can have an impact on the economics of mine development.
Planning and mitigation: Detailed descriptions of exploratory cores and surface exposures of the mined coal, and analyses of coal seam and parting thickness profiles from mine maps and cores in surrounding areas are generally adequate for predicting and planning for the occurrence of partings in a coal bed. In surface mines, partings may be removed systematically during mining. In underground mines, they must be mined with the coal and removed in preparation plants.