Mineral liberation, association and textural information about processed iron ore is vital for understanding and predicting iron-ore downstream processing performance. Such information is usually obtained by two major imaging techniques – Optical Image Analysis and Scanning Electron Microscopy. Both techniques use polished epoxy resin blocks with embedded sized particles suitable for imaging. Each particle section can be classified to a certain liberation or textural class. If the amount of analyzed particle sections is sufficient for statistical validity, the abundance of particles in each class gives an objective description of the whole sample.
Different particle sections in the block can touch each other and the processing software may consider such particles as just one particle. If the touching particles belong to different liberation or textural classes this will most probably result in distortion of the liberation, association and textural data of the sample.
CSIRO developed the new Mineral4/Recognition4 software for textural characterization of different ores, sinters and coke with a novel image analysis processing routine for separation of touching particle sections. This processing is based on two major methods: modified watershed separation and modified binary erosion separation. Depending on the ore type, particle size, imaging magnification and other factors, both methods can be adjusted to obtain a better final result. The article highlights the negative effect of particle touching, the importance of separation, and improvements made by distinct methods to incorrect separation by comparing different cases, including those when touching particles are not separated at all, separated manually and when they are separated automatically by each method, or their combination, with different options. The article demonstrates the effects that touching particle sections have on liberation and textural iron-ore characterization and shows that the proper use of automated separation developed within the Mineral4/Recognition4 system significantly reduces errors introduced by touching particle sections.