Coal breaker the United States in the state of Pennsylvania (where, between 1800 and the mid-20th century, many of the world's known anthracite reserves were located). At least one source claims that, in 1873, coal breaking plants were found only at anthracite mines in Pennsylvania. The first function of a coal breaker is to break coal into pieces and sort these pieces into categories of nearly uniform size, a process known as breaking. The second function of a coal breaker is to remove impurities (such as slate or rock), and then grade the coal on the basis of the percent of impurities
Coal breaker 19th century and early 20th century led to the use of mechanical devices for separating impurities from coal in coal breakers. Screens and sorters were used for dry coal. Some examples from the beginning of the 20th century are: To handle wet coal, coal jigs were used. Coal jigs separated coal from impurities by using gravity. Since the relative density of uniformly sized pieces of coal, slate, ash, dirt, and sulphur vary, pieces of each element will descend through water at different speeds—allowing them to be separated. Some examples of coal jigs from the beginning of the 20th century include: