Magnesium Carbonate
What it does
Anti-caking, acidity regulator.
How it's made
Mined or manufactured.
Magnesium carbonate is a white mineral salt used in food as an anti-caking agent to keep powders free-flowing, as an acidity regulator, and as an anti-clumping coating (famously on the salt that climbers and gymnasts use). It is the same basic compound as the mineral magnesite.
Food-grade magnesium carbonate is usually made from purified mineral sources of magnesium. A common route dissolves magnesium salts and then precipitates magnesium carbonate by reacting a magnesium solution with a soluble carbonate such as sodium carbonate; the light, fluffy solid that forms is well suited to soaking up moisture and preventing caking.
The precipitate is filtered, washed and dried into a very light white powder. Because it is made by precipitation from purified solutions rather than simply ground from ore, food-grade magnesium carbonate is consistent and clean, and its high surface area is what gives it its excellent moisture-absorbing, free-flow properties.
Possible reactions
Generally safe; mild laxative in quantity.