Class F planet

Class F Geometallic
Young planets, Class F worlds range in age from 1 to 3 billion years old. Their diameters range in size from 10,000 to 15,000 km. They are located in the biozone region of a star's solar system. Their surfaces are actively volcanic. Their atmospheres primarily contain hydrogen compounds. Class F planets cool over time to evolve into Class G worlds. Life forms, if any, are silicon based.

Example: Janus VI