An automatic particle segmentation system is developed for calculating the size distribution of rock fragments created by blasting. A rock composite due to blasting is often fully multi-connected in which individual particles cannot be delineated by the existing segmentation algorithms. Two algorithms are proposed to approach this multi-connected segmentation problem. The first algorithm analyzes the shape of each shadow (a simply-connected region) and "splits" the particles from shadow boundary convexity points if a relatively large gradient path occurs. The second algorithm finds clusters of rock particles which may not be delineated due to the lack of a strong gradient along the touching portions and delineates them using a shape heuristics. A large number of test results show that the method is fast and accurate.