The Sun is symbolised by the circle and reflects the active principle of being, the pure act of essence. This is the planetary symbol of the King. Gold the metal associated with the Sun represents pure spirit embodied in mineral form.
The Moon is symbolised by the crescent or semi-circle and reflects the passive principle of becoming, constant change. This is the planetary symbol of the Queen. Silver is associated with the Moon and represents the metal whose purity is like the purified soul able to reflect spirit in all its glory.