Alginite

Alginite is a component of some types of kerogen alongside amorphous organic matter. Alginite consists of organic-walled marine microfossils, distinct from inorganic (silica)-walled microfossils that comprise diatomaceous earth. At least two forms of alignite are distinguishable, "alginite A" and "alginite B". The "A" form contains morphologically distinguishable microfossils while the "B" form is more amorphous and film-like.