Helicon
From Tardis Wiki, the free Doctor Who reference
Helicon was a mineral that was not highly valued. Its low conductivity and strength meant that demand for commercial or industrial use was also low.
However, when in liquid state Helicon 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)
