Onyx and Pitch dark

Onyx noun - A chalcedony with alternating black and white bands; used in making cameos.

Pitch dark and onyx are semantically related In some cases you can use "Pitch dark" instead an adjective "Onyx".

Onyx and pitch dark are semantically related in black topic. Sometimes you can use "Onyx" instead an adjective phrase "Pitch dark", if it concerns topics such as dark.