Obsidian and Pitch-black

Obsidian noun - Acid or granitic glass formed by the rapid cooling of lava without crystallization; usually dark, but transparent in thin pieces.

Pitch-black and obsidian are semantically related in black topic. In some cases you can use "Pitch-black" instead an adjective "Obsidian".

Pitch-black adjective - Being without light or without much light.

Obsidian and pitch-black are semantically related in black topic. Sometimes you can use "Obsidian" instead an adjective phrase "Pitch-black".