Lasso durability

Diana looped a coil around her hand and flung the rope into the fire, sending up a shower of sparks.
Alia gasped, but the lasso didn’t catch.  It lay in the flames, unaltered, visible through the fire like a stone through clear water.
Diana drew it back and passed it to Nim.  “See?” she said.
Nim squealed.  “It’s not even warm!”