There are geological concretions, but not all concretions are geological. Only one style of concretion is geological, all others including geodes are biological. I show you the difference in this video. I will show you how certain minerals are drawn to a biological nucleus center that make up a geological concretion, and you wont find "nor should you" this type nucleus center of a Biological Process. Geology does not know the difference and believes they are all geological process. 100% WRONG!