Is Epsom salt a pure substance?

Epsom salt, chemically known as magnesium sulfate heptahydrate (MgSO₄·7H₂O), is considered a pure substance when it is in its crystalline form. It consists of specific proportions of magnesium, sulfur, oxygen, and water. However, if mixed with impurities or other substances, it would no longer be classified as pure. Thus, Epsom salt is a pure compound when it is free from contaminants.