Elven chain mail has long been a staple of Fantasy Role-Playing games, and fiction based upon them. It is made from a secret elven alloy, and generally weighs less than half of what normal chain mail does. Some elven spellcasters can even wear this armor while casting spells, although this varies from game to game.
The construction of elven chain is the most closely guarded secret of the elven race. The few who hold its secret will die before ever revealing it to the wrong eyes. Only the most wise and skilled elven armorers can make this legendary chain. There are never more than a few elves alive at any one time who know how to make this chain. Combine this with the elves 1400 year lifespan, and you get a secret that has only ever been known to a handful of elves. Being chosen as the apprentice of one of these armorers is the highest honor that any elf could ever hope to receive. Wealth and social standing seem to have no bearing upon who is chosen for apprenticeship. The selection is said to be magical in nature, either you have the gift, or you don't, and all the money in the world can't change that.
What is known is that the armor is made of mithril alloyed with several unknown metals. Researchers say that magical manipulation may be needed to manufacture the alloy, as humans and dwarves have been unable to properly duplicate the metal. There is no real hope of duplicating the armor anyway, as it takes even an elf almost 800 years to learn the art, no other race lives long enough to even hope to learn. It is said to take over 10 years just to craft a single suit of this armor.
Elven chain mail is most common among the grey elves, and other more advanced elven cultures. It is almost unknown among the more common wood elves that make up the majority of the elven population. This armor is almost never made to fit anyone other than an elf, despite what the treasure tables may say. There are perhaps a few dozen human sized suits of this armor on any given world, and even less than that of dwarven or gnomish sizes.
Sometimes elven chain will be enchanted to have even more special properties. There are only a few suits of this magical elven chain in existance. Almost all of them in the hands of ancient elvish lords and heroes. This armor is so light that it can be worn like normal clothing. It can be worn without hindering spellcasting or thief abilities. There is no magical item more rare than magical elven chain. Many heroes have died searching for it.