Mass Effect 2 & Mass Effect 3
Asari-made Silaris armor can resist even the tremendous heat and kinetic energy of starship weapons. The armor is nearly unsurpassed in strength because its central material, carbon nanotube sheets woven with diamond Chemical Vapor Deposition, are crushed by mass effect fields into super-dense layers able to withstand extreme temperatures. That process also compensates for diamond's brittleness.
Diamond armor itself has two limiting disadvantages. First, while nanotubes and CVD-diamond construction have become cheaper in recent years, it remains prohibitively expensive to coat starships or aircraft larger than fighters in Silaris material. Second, the armor must be attached to the ship's superstructure, so shock waves from massive firepower can still destroy the metals beneath the armor itself.
A popular misconception holds that the diamond composition of Silaris armor gives it a sparkle. In fact, atmospheric nitrogen impurities during the super-hot forging process give the armor a metallic gray or yellow sheen.