Fire Moss

Fire Moss is a moss plant plant that grows on stone blocks in the lava layer. Fire Moss glows slightly and sprouts glowing fuzz that can be cut like grass weeds. Stone covered in Fire Moss requires one more hit to break than clean stone, but otherwise does nothing. Fire Moss will be destroyed if the stone block it is on becomes ebonstone, crimstone, or pearlstone.

Spread
Fire Moss slowly spreads across exposed stone blocks. Although there are no moss seeds, a player can grow extra moss by building "bridges" of stone for existing moss to grow across. Fire Moss cannot grow above zero depth.