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Basalt

/bəˈsɔːlt/noun

A dark, fine-grained volcanic rock that makes up most of the ocean floor.

The Greek roots

βάσανος
básanos
touchstone, test

Literally: touchstone rock

Follow a root:βάσανος1 word

The story of the word

Pliny wrote basaltes for a hard dark Egyptian stone, apparently a slip for Greek βασανίτης, the assayer's touchstone that gold was rubbed against to test its purity. Because a false coin could be exposed that way, βάσανος also came to mean an ordeal, and then interrogation under torture. The Greek word is thought to be a borrowing from Egyptian to begin with. When basalt cools slowly it contracts into hexagonal columns, which is what the Giant's Causeway is.

How it travelled
Ancient Greek → Latin → English
First recorded
17th century

In a sentence

The whole headland is basalt, black and squared off like masonry.

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