| 21. | All delay boxes on the market were quartz crystal accurate by the year 1990.
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| 22. | In 1948 researchers at Fort Monmouth grew the first synthetically produced large quartz crystals.
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| 23. | The quartz crystal is temperature compensated and is hermetically sealed in an evacuated envelope.
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| 24. | Devils Head is most noted for large topaz crystals and even larger smoky quartz crystals.
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| 25. | Smoky quartz crystals and topaz are found in many places in the Pikes Peak granite.
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| 26. | Examples of xenocrysts are quartz crystals in a silica-deficient lava and diamonds within kimberlite diatremes.
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| 27. | Many clocks keep time by mechanical resonance in a balance wheel, pendulum, or quartz crystal.
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| 28. | Quartz crystals are manufactured for frequencies from a few tens of kilohertz to hundreds of megahertz.
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| 29. | In modern designs it is common to use quartz crystal filters, especially for narrowband filtering applications.
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| 30. | Atomic clocks, which rely on the oscillations of atoms, not quartz crystals, are far more precise.
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