¹ Then the Lord said to Moses and Aaron, “Take handfuls of soot ²  from a furnace, and have Moses throw it ³  into the air while Pharaoh is watching. ⁴ 

So they took soot from a furnace and stood before Pharaoh, Moses threw it into the air, and it caused festering boils to break out on both people and animals.

ח (Khet) Now their appearance ¹  is darker than soot; they are not recognized in the streets. Their skin has shriveled on their bones; it is dried up, like tree bark.