Helicon
From Tardis Wiki, the free Doctor Who reference
Helicon (mineral alloy RL225) was a mineral that was not highly valued. It had low conductivity and low strength, causing it to be in low demand for commercial or industrial use.
However, when in liquid state it could record the brain patterns of a psychic. Xais used it to copy her mind before her execution on the Rock of Judgement into a helicon death mask. Three years later, she gained enough strength to take over Margo, the Rock's chief of security. (PROSE: The Romance of Crime)
