I have heard that Zechstein Miracle is beneficial for skin conditions such as psoriasis and eczema?

This is correct. Zechstein Miracle magnesium products are highly therapeutic and healing to skin conditions such as Psoriasis, Eczema, Dermatitis, Acne, Poison oak etc.
Directly applied magnesium chloride enhances skin barrier function, decreases inflammation, speeds wound healing, and increases skin cell hydration. However, if you have broken skin or a large portion of your body is affected, it is advised to begin your healing regimen with magnesium baths until the skin has had a chance to start healing and become less sensitive to the high concentration of magnesium salts in the magnesium gel, magnesium lotion and magnesium oil.