十万个为什么·科学阅读30篇（1）

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为什么某些岩石在紫外线照射下会发光？

Some minerals like fluorite and calcite absorb invisible ultraviolet light and re-emit it as visible light.
This process is called fluorescence, and it happens because electrons in the mineral jump to higher energy levels.
When those electrons fall back down, they release energy in the form of colored light we can see.
The specific color depends on the mineral’s chemical composition and tiny impurities inside its crystal structure.
Not all rocks glow—only those with fluorescent elements such as uranium, manganese, or rare-earth metals.
Scientists use UV lamps to identify minerals in fieldwork and geological surveys accurately.
Fluorescence differs from phosphorescence because the light stops immediately when the UV source is removed.
Even though UV light is harmful in large doses, the small amounts used for rock testing are safe.
This natural phenomenon helps researchers understand how minerals formed deep underground over millions of years.
Glowing rocks remind us that Earth holds many hidden optical secrets waiting to be discovered.