chert bed
层状燧石 bedded chert
燧石砾层 [地质] flint gravel
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燧石本质是含有黑耀石的石英，只有在诺福克郡南岸的白垩层中才能看到。
Flint is a quartz related to obsidian, and is found only in the chalk seam that extends from the south coast to Norfolk.
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