An iron-60 crystal matrix is a phaser matrix designed from iron (isotope 60).
During a midnight planning and brainstorming session called on the USS Enterprise-E by second officer Miranda Kadohata, Rennan Konya suggested that an iron-60 matrix would be required to allow ship-mounted phasers to fire transphasic energy, matching the effectiveness of the transphasic torpedo. However, such a matrix would not allow for sufficient energy levels to be effective. (ST - Destiny novel: Gods of Night)