Glistening beans during roasting

Hi,

I'm fairly new to chocolate making. I was making my 11th batch yesterday and, for the first time, used Ghana (washed) beans. During the roast process (started at 150C and ended at 130C) some of the beans started to "glisten". It was almost like some cocoa butter had provided a sheen to the surface of the bean but it did not seem to rub off when I ran my fingers over it. Also, it was only some of the beans (maybe 10-20% of total being roasted) and they were fairly evenly spread across the roasting tray. The "glistening" only happened on the beans after the roast started.

Has anybody seen this before? Is it normal? Does it indicate anything about the beans?

Thanks