| A microcrystalline form of silica also called hornstone |
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| Silica rock |
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| Hard microcrystalline or cryptocrystalline form of silica resembling, and sometimes synonymous with, flint (5) |
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| Rock of which flint is a variety |
The Times Specialist |
18 Nov 2024 |
| Quartz rock |
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| Variety of silica that contains microcrystalline quartz |
The Telegraph General Knowledge |
15 Mar 2021 |
| Siliceous rock often occurring as flint nodules in chalk |
The Guardian Speedy |
23 Aug 2020 |
| Rock with that lady in Connecticut |
The Telegraph Toughie |
27 Sep 2019 |
| Event that's sure to include hard rock |
The Times Cryptic |
26 Jun 2015 |
| Rock like flint |
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| Fine-grained silica |
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| Rock found in limestone beds |
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| Flintlock rock |
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| Flintlike rock |
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| Quartz |
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| Fine-grained rock |
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| Flint-like rock. |
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| Dull-colored flintlike quartz. |
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| Flintlike quartz. |
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| Kind of quartz. |
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