Moonstone
From Shadow of the Throne Wiki
Appearance: A soft milky white stone, with a beautiful rolling sheen. This sheen has a rainbow-like array of colors, which shift and change to complement the colour of the bearer’s clothing, as well as a glow that matches the current phase of the moon in intensity. The stone resembles little more than a cheap pebble during Calibration.
Description: Moonstone is regulated in the Realm, where mortals are barred from possessing it. It is found as part of many ancient instruments designed to keep track of time in the long-term. A moonstone costs R4.
Large concentrations of moonstone can be melted down and concentrated to form iridescent filaments of use in essence circuitry designed to simulate thought and process computations.