Crem

Crem is the sludgy brown material that falls with the rain. Highstorms carry it across all of Roshar, and cremlings are never far from it. Water with crem in it will make a person sick, so it has to stand for a day until the crem settles to the bottom and the drinkable part can be poured off the top, and even then it tastes metallic. Otherwise it behaves a good deal like clay. It molds, so it turns up as pottery and as filler for small holes in grain polyps, and older or more remote communities build with it, mixing it with stone or shaping crem bricks. Left alone it hardens into stone, which is why buildings grow stalactites where stormwater drips from the eaves, and why those have to be cleaned off before they weigh a roof down enough to collapse it.