Munsell color value as related to organic carbon in Devonian shale of Appalachian basin

Comparison of Munsell color value with organic carbon content of 880 samples from 50 drill holes in the Appalachian basin shows that a power curve is the best fit for the data. A color value below 3 to 3.5 indicates the presence of organic carbon but is meaningless in determining the organic carbon content because a large increase in amount of organic carbon causes only a minor decrease in color value. Above 4, the color value is one of the factors that can be used in calculating the organic content. For samples containing equal amounts of organic carbon, calcareous shale containing more than 5% calcite is darker than shale containing less than 5% calcite.