I melted about 2 kg of gallium and put it in a plastic container, in order to make crystals. After letting them grow and extracting them, I let the gallium freeze at the room temperature, which is below the melting point.
However, for some reason there is a small quantity of gallium (10-20 g) that is not freezing after days. I extracted the liquid then froze it in a refrigerator. But if I put it outside again, it melts, so this is not supercooled gallium, a well documented phenomenon.
It behaves like normal gallium with slightly lower melting point, something like a Galinstan eutectic. However this is 99.99% pure gallium (that was fully solid) and I am pretty sure that I never contaminated it...
Any idea what is happening?