2017年4月6日星期四

A kind of gravel is best seen in a dark area

The glow of photoluminescent tumbled gravel is best seen in a dark area, where ambient light sources such as streetlights and moonlight are absent. The glowing stone is non-toxic, non-radioactive, eco-friendly as they require no batteries and no wires. They will last for years charging over and over again.  

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