magma
A magma is a thick, milky, slightly gloopy suspension of very fine insoluble mineral particles in water — the classic example being the chalky white liquid antacid you shake before drinking. The word borrows the geological sense of a thick, pasty mineral mass.
Technically a magma is a viscous aqueous suspension of fine, insoluble inorganic particles, often with the particles so small and so highly hydrated that they form a loose gel-like network giving the product its characteristic body. Unlike a coarse suspension, the very fine, colloid-scale particles and their water-binding give a magma its thick, creamy consistency, which itself helps slow the particles from settling out.
Magmas are mostly used as antacids and as bulky gastrointestinal agents, where a large surface area of insoluble mineral is exactly what is wanted. Like any suspension they must be shaken before use, because the dispersed solid will still settle over time; the gel-like structure slows this but does not abolish it.
Milk of Magnesia is a magma of magnesium hydroxide in water, used as an antacid and laxative; the fine insoluble particles must be shaken back into uniform suspension before each dose.
A thick milk of fine insoluble mineral particles, shaken before each antacid dose.
A magma is really a special, very fine, gel-like suspension; its thick consistency comes from highly hydrated colloidal particles, which slows but does not stop settling, so it still needs shaking before use.