What the fuck is this?

I bought gallium many years ago just to fuck around with.
Since then I stored it in a non-airtight container.
I assume the dark grey layer on top is an oxide layer, but why is there a liquid component well below it's melting point?
Current ambient temperature is probably around 24C.

I'm pretty sure it's pure gallium since I originally stored it in the freezer and it was completely solid at that point. I currently have it in the fridge to see if it will turn solid at a lower than ambient temperature.