# obsidian

/əbˈsɪdiən/ (US) · /ɒbsˈɪdiən/ (UK) · CEFR C1 · Noun

Source: https://englishreference.com/word/obsidian
Updated: 2026-05-18

## Definition

a shiny black rock that is actually a type of glass. It forms when lava cools very quickly and is used to make sharp tools or jewelry.

For teachers: a naturally occurring volcanic glass formed by the rapid cooling of lava from a volcanic eruption. It is typically black in color and possesses a smooth, glassy surface.

## Examples

- The ancient people used obsidian to make very sharp knives.
- Archaeologists found a shard of obsidian at the site, suggesting that the inhabitants traded with distant volcanic regions.
- The polished surface of the obsidian mirror reflected the room with such clarity that it seemed to disappear into the darkness of the stone.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.