There is provided herein a process for the compaction of Polyhalite with a Potassium salt, wherein said process comprising: mixing a feed of polyhalite with a feed of said Potassium salt in a mixer to yield a mixture; compacting said mixture in a compactor to yield masses; crushing said masses in a crusher to yield particles; screening said particles in a screener to yield fine particles in three different sizes: oversized fine particles which undergo a second crushing process and are retuned to said screener for screening, undersized fine particles which are transferred to said mixer for further mixing, and desired size fine particles which are transferred to a polish screener glazing, drying and oiling.