If you are looking for the Element of Plasma, go here.
The Element of Melting was a strange purple crystal that could be found in Ko-Wahi. It could be used to quickly turn ice into pure water for the Ko-Koro water supply. Takua had to find the Element of Melting during his search for the Toa Stones on Mata Nui.
- BIONICLE: Quest for the Toa (First appearance)