Organic (Organogenic) Soil

The soil is classified as organic silt or organic clay if the liquid limit after oven drying is less than 75 % of the liquid limit of the original specimen determined before oven drying. A further classification of organic fine grained soils (group symbols OL and OH) is presented in a future section [ASTM D2487-06].

Another organic soil type is peat, that consists of "primarily vegetable tissue in various stages of decomposition usually with an organic odor, a dark-brown to black color, a spongy consistency, and a texture ranging from fibrous to amorphous [ASTM D2487-06].