Hi Fred
It looks like it could be one of the very small Phoenix berries that are essentially the same colour as the soil or slightly darker. It however does not seem to have the characteristics of a meridiani berry. It could be that it is indeed covered in mud.
The "berries" in my reply 328 seem to have been left after the soil dried out from soil spills left on the PHoenix deck. There are so many of them that I think a closer look is warranted. They might turn out to be just soil particles on closer examination but there is a possibility that they might not. I don't think there is any harm in checking them out in the now extended mission which seems to have a renewed fervour for exploring any aspects of life that could be examined.
Winston