The final degree project for a Bachelor of Science in Mining and Mineral Engineering has been carried out at Boliden Mineral AB between April and June 2013.The report describes the history and geology of the mines of Boliden, origin and the development of one of the largest metal-mining companies in Europe - Boliden Mineral AB.In the Boliden area there are many important ore fields which contain gold, zinc, copper, silver and lead.The objective of this project was to investigate and provide the guidelines for the improvement of the regrinding in the ball mill in the Concentrator flotation circuit having influence on metal recovery.The report follows the ore flow from the mine, through the Concentrator and finally to the end product, concentrates. The evaluation leads to conclusions which parameters may affect the concentration process negative.It was discovered that there are problems with the ore stockpiles at the mine and the segregation of the fractions in the silos. It is proposed to install a cone on the top of the silos to reduce segregation of ore fractions. To reduce this problem Boliden should install a mobile conveyor on the way to the silos and to the ore stockpiles in the mine. This method has been successfully installed at the Aitik ore stockpiles near the new Concentrator.The main task of the thesis was to analyze metal distribution in the flotation circuit, especially technical analysis of regrinding effects on the results of flotation. The analysis of the sampled pulp from the flotation process was done in the Mineral Processing Laboratory and in the Process Laboratory in Boliden. The analytical equipment such as X-rays and ICP were used for metal analysis and QEMSCAN was used for mineralogical determinations analyses.Theoretical calculations and results of conducted laboratory experiments suggests that regrinding in the ball mill has a positive effect on the flotation process, but some improvement is required, especially the regrinding of the gangue particles. This process helps to liberate all metal particles and improves results of metal recovery. For improvement of regrinding process, it is proposed to replace the regrinding ball mill with a newer, more efficient mill of SMD type (Stirred Media Detritor). / <p>Validerat; 20131218 (global_studentproject_submitter)</p>