Magnesium Oxide occurs as a white to off-white powder, it is known as Heavy Magnesium Oxide. It is soluble in dilute acids, practically insoluble in water, and insoluble in alcohol. It is easy to absorb the moisture and carbon dioxide in the air. It’s also classified as magnesium oxide https://www.richen-nutritional.com/magnesium-oxide-powder-food-grade-for-magnesium-supplementatioin-product/