Give a stream of consciousness and then the final answer. Magnesium sulfate is an inorganic salt with the formula MgSO (H O) where 0 x 7. It is often encountered as the heptahydrate sulfate mineral epsomite (MgSO 7H O), commonly called Epsom salt. The overall global annual usage in the mid-1970s of the monohydrate was 2.3 million tons, of which the majority was used in agriculture.

Answer this question: what is the chemical formula of epsom salt?
This is the relevant information: It is often encountered as the heptahydrate sulfate mineral epsomite (MgSO 7H O), commonly called Epsom salt.
So, the final answer is MgSO 7H O.