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# obsidian

«obsidian» in Mova's school dictionary: **a hard, shiny black (or dark) natural glass that forms…** — its meaning for a pupil, its sense in the lessons and examples, with 4 sentences of Mova's corpora that use it.

### part of speech

noun (obsidian; uncountable)

### meaning for a pupil

1) Obsidian is a hard, shiny black (or dark) natural glass that forms when lava from a volcano cools very quickly. [tree →](https://md.mova.elamur.ai/free/en/corpora/dictionaries/school/O/obsidian/#m1)

2) Obsidian was used long ago to make very sharp knives, arrowheads and mirrors. [tree →](https://md.mova.elamur.ai/free/en/corpora/dictionaries/school/O/obsidian/#m2)

### sense in the lessons

In science lessons on rocks, obsidian is an igneous rock (made from cooled lava) that cooled too fast for crystals to grow, so it is glassy; when it breaks it has very sharp curved edges. In history, the Aztecs and other peoples made tools and mirrors from it. In the game Minecraft, obsidian is a very hard block. Phrases: «obsidian blade», «volcanic glass».

### examples

- Obsidian is black volcanic glass. [tree →](https://md.mova.elamur.ai/free/en/corpora/dictionaries/school/O/obsidian/#x1)
- Obsidian forms when lava cools very quickly. [tree →](https://md.mova.elamur.ai/free/en/corpora/dictionaries/school/O/obsidian/#x2)
- Ancient people made sharp arrowheads from obsidian. [tree →](https://md.mova.elamur.ai/free/en/corpora/dictionaries/school/O/obsidian/#x3)
- The museum had an Aztec mirror made of obsidian. [tree →](https://md.mova.elamur.ai/free/en/corpora/dictionaries/school/O/obsidian/#x4)
- In Minecraft you need obsidian to build a portal. [tree →](https://md.mova.elamur.ai/free/en/corpora/dictionaries/school/O/obsidian/#x5)
- Obsidian is an igneous rock. [tree →](https://md.mova.elamur.ai/free/en/corpora/dictionaries/school/O/obsidian/#x6)

### note

Uncountable: «a piece of obsidian». Pronounced ob-SID-ee-un. Safety: broken obsidian is sharper than a knife, so handle with care.

### In the corpora

- [Lightning striking sand can melt it into glass tubes called fulgurites; volcanoes make a natural black glass called obsidian.](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/30-glass-and-pottery/11/)
- [Obsidian is natural glass that forms when lava cools so fast that no crystals can grow.](https://md.mova.elamur.ai/free/en/corpora/school/geography/48-igneous-rocks-and-the-rock-cycle/10/)
- [Sharp volcanic glass called obsidian travelled hundreds of kilometres over 10,000 years ago.](https://md.mova.elamur.ai/free/en/corpora/school/history/70-trade-why-people-swap-and-the-great-trade-routes/10/)
- [Obsidian, a sharp volcanic glass, was traded over long distances more than 10,000 years ago, before the first cities.](https://md.mova.elamur.ai/free/en/corpora/school/history/70-trade-why-people-swap-and-the-great-trade-routes/14/)

### Trees and pragmatics

[Every meaning and example of «obsidian» parsed by Mova](https://md.mova.elamur.ai/free/en/corpora/dictionaries/school/O/obsidian/), each sentence with its dependency tree and frames.