Coal petrography vocabulary: A coal containing a very high percentage of durain (the dull, hard lithotype rich in inertinite) is commonly termed ________ coal.

Introduction / Context:
Coal is described using macroscopic lithotypes: vitrain (bright), clarain (banded), durain (dull), and fusain (fibrous). These reflect maceral composition and depositional history, which in turn affect caking, coking, and combustion behavior. Identifying a coal dominated by durain helps anticipate its performance in carbonization and gasification.

Given Data / Assumptions:

• Durain: dull, hard lithotype, inertinite-rich, poor caking.
• Vitrain: bright, vitrinite-rich, better caking behavior.
• Terminology uses historical industrial names: “splint coal” is associated with high durain content.

Concept / Approach:

Coal with abundant durain tends to be hard, dull, and non-caking; it fractures splintery—hence the name “splint.” Such coals are less suitable for metallurgical coke but can be used for domestic fuels or gasification where caking is not required. In contrast, “bright coal” refers to vitrain-rich material with better coking tendencies. Boghead/cannel coals are algal or sapropelic and are distinct from durain-rich banded bituminous coals.

Step-by-Step Solution:

Verification / Alternative check:

Petrographic references and coke-oven practice consistently associate splint coal with poor caking and a high proportion of dull bands (durain).

Why Other Options Are Wrong:

Bright/vitrain-rich coals are the opposite texturally; boghead and cannel describe sapropelic coals formed from algal material; “non-banded” does not specifically indicate high durain content.

Common Pitfalls:

Confusing maceral groups with lithotypes; assuming “bright” refers to calorific value rather than appearance and petrography.

Final Answer:

Splint coal (durain-rich, hard, non-caking)