We just brewed an all grain batch yesterday. There was an ounce each of two types of whole leaf hops (from Freshhops) in the boil. After cooling the wort, we strained it through a fine mesh strainer into a bucket before racking into a carboy for fermentation. There were small black balls, about the size of coriander seeds, in the strainer.
My first knee-jerk thought was that something had fallen into the batch during the boil, but this is completely implausible, as the boil took place indoors in a clean environment and was attended most of the time. The only other thing I can think of was that these were seeds from the hop plant that made it through processing and packaging.
We almost always use whole hops and this method, and I have never seen anything like this before. (I'm not worried; just curious.) Has anyone encountered this before?