I believe they are hardwood pellets used in pellet grills. I've never turned one but often times when you cast something harder than the resin you will have that issue, especially since there are so many and less resin. The pellet construction could also be the problem. To help you can saturate the blank a few times during the turning process with thin CA. That may help hold them together along with the usual sharp tools and light touches. Sadly not all blanks turn the same and some make us work a little harder.