The final, thirteenth class includes organic substances that can be considered minerals. These are citrates, oxalates, and acetates that form through the reaction of metallic cations with the corresponding organic acids, under the influence of natural physical-chemical processes that occur without human or other living organisms' influence.

Notable representatives of this class include whewellite, weddelite, and melilite. This class also includes hydrocarbons, of which fichtelite can be considered a mineral, while petroleum, tar, ozokerite, asphalt, and various types of coal (anthracite, bituminous coal, brown coal, lignite, and peat) are considered rocks. In the past, organic compounds with oxygen that are not salts were also included in this class. These include fossil resins, with amber being the most famous.