Hydrocarbon-containing organic matter is extracted from a hydrocarbon-containing material that is a viscous liquid, liquid or gaseous fossil fuel material. A turpentine liquid is contacted with a hydrocarbon-containing material in-situ in an underground formation containing the fossil fuel material to form an extraction mixture so as to extract hydrocarbon-containing organic matter into the turpentine liquid and form an extraction liquid. The extraction liquid is removed from the formation, the extraction liquid including the turpentine liquid containing the extracted hydrocarbon-containing organic matter. The extracted hydrocarbon-containing organic matter is separated from a residual material not extracted.