All organic macerals with lower reflectance than inertinite, and higher reflectance than liptinite are usually given the generic name vitrinite, and their reflectance is measured. For Ro measurements from coals, the situation is a little better, because hydrogen-rich vitrinite, such as desmocollinite, and hydrogen-poor vitrinite, such as pseudovitrinite, can be distinguished by comparing their reflectance and relief with those of telocollinite and semi-fusinite, which can be found easily in most humic coals. However, the problem still exists to some extent, because even the telocollinite in coals with high contents of desmocollinite or pseudovitrinite has relatively higher or lower initial hydrogen contents than that in “normal” coals.

In very good oil source rocks and coals deposited under marine influence, vitrinite macerals have higher initial hydrogen contents and lower maturation rates, and thus lower Ró values and, even with the same thermal histories, smaller ∆Ro values than telocollinites (on which Ro for coals is usually measured in “normal” coals). Thus, very good oil source rocks and marine coals will have highly-suppressed Ro values.

Thanks Onimisi