Solved cryptogram
Big crystals in a rock mean the melt cooled slowly, and tiny ones mean it cooled in a hurry.
Earth Science Facts, sourced to U.S. Geological Survey.
Solve it yourself
This fact is a cryptogram here: 72 letters over 19 different ones, graded medium.
Or go to the puzzle’s own page first.
What it means
Atoms need time to find their places in a growing crystal. Magma trapped kilometers down loses its heat over thousands of years and grows grains you can pick out with the naked eye, which is why granite looks speckled. The same melt reaching the surface as lava freezes in days and leaves crystals too small to see. So a hand lens reads the history of a rock: the texture is a thermometer with a clock attached.
The claim comes from U.S. Geological Survey.
- SourceU.S. Geological Survey
- CollectionEarth Science Facts
- Difficultymedium
- Length72 letters, 19 of them different
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