From Exalted - Unofficial Wiki
Starmetal, as-written in the book, is rather at odds with both the stylings of the Sidereals and the magical materials themselves. Orichalcum is made from gold smelted with magma and occult mirrors reflecting sunshine; Moonsilver comes from moonlight condensing Wyld essence into a metal; Jade is elemental energy.
And yet Starmetal is close to Soulsteel as the Corpse of a God, painting Sidereals as mustache-twirling divine murderers if they want any artifacts at all. Nothing to do with actual fate, just the execution and defiling of a divine body. Finding this objectionable and simply villainization, I thought I'd design an alternate version, which goes more in line with their role as servants of Fate.
As threads of fate weave through the loom, they pick up the auspicious essence of Fate Gone Right; all the joys, travels, conflicts, revelations, and conclusions of the person living their life accumulate into a faint crystalline metal built up upon the thread. Only after the target dies of properly fated causes does this crystalline structure become fully metal, and trim properly rather than shattering into dust if cut early. These castoff trimmings are accumulated and melted down in a specially prepared smelter in the Bureau of Destiny building, forging ingots of a deep, iridescent steel-like metal known as Starmetal.
Unfortunately, despite the countless mortals living and dying lives of little meaning every year, the starmetal produced by such is very lacking. The thread of a mortal without any Destiny bears little more than a dusting of the fatewoven crystal that becomes metal. An entire decade's worth of properly fated deaths bears enough starmetal on its' own to make up a tiny fraction of the least of artifacts; for the creation of more powerful artifacts in any sense of timeliness, Destinies are required.
A destiny of appropriate rating provides starmetal of sufficient purity to count as a component for an artifact of equal rating. Of course, these destinies carry two difficulties. First, Destinies tend to disrupt fate, as those blessed by Destiny tend to stop fights, disrupt happiness, interrupt travels, reveal secrets, and prevent deaths simply by dint of being so important as to have their will affect the world. Secondly, the bearer of the Destiny has to live to their fated time of death, lest the nascent starmetal shatter on the thread when cut. Saturn is very cynical when it comes to important, fated deaths, and rarely approves powerful destinies for people to die in anything short of what she decides is the proper time for a death.
The Bureau of Destiny possesses a reserve of starmetal ingots both as an emergency reserve and for the use of its' agents, permitting a Sidereal to petition for the creation of an artifact without requiring decades of waiting for an appropriate destiny to come to fruition. However, this contractually obligates the Sidereal to create at least one destiny of equal value in order to replace the precious ingot, and to tend to it and clean up any errors in its' wake. Dereliction of this duty tends to induce censure.