Godstone

While dwarves have a monopoly on the greatest metal alloys in Kytheria, elves have a unique substance all to themselves, the bizarre substance known as 'godstone'. Though it comes in myriad forms from hard, dense bricks to spun thread, as far as any non-elven sages can determine this magic material emerges from special elven temples and is made from nothing but sunlight and air. Elves, as in all things, remain tight-lipped about this fabric.
Though it can take the place of silk in some kinds of armor, godstone is typically woven with natural fibers to gain the benefits of both materials. Elven clothing not only has incredible longevity (a necessity for this race) but helps adjust to myriad temperature conditions, wicking moisture away from sweating bodies and releasing it to evaporate. Elven parachutes are made entirely from this stuff, and elves are the only people who regularly include these inventions as safety features on skyships.
Godstone sails also grace elven vessels, and the abundance of the material means it also decorates homes and shops (some of which are constructed from godstone bricks). It's proven to wear down less easily than stone when constructed as bricks, and doesn't rot or otherwise decay.

Properties

Material Characteristics

Often seen as a dull or matte gray, special dyes are made for this material specifically, allowing the color to vary considerably.

Physical & Chemical Properties

Godstone doesn't hold moisture easily, and one unfortunate aspect of it is the tendancy to melt rather than burn. Elves who deal with fire consistently avoid this material as a rule.

Compounds

The sages are correct; godstone is spun from sunlight and air. Specifically, carbon dioxide in the atmosphere is collected and solar energy powers the magical process which fuses carbon together in long chains.

Geology & Geography

Because godstone is exclusive to the elves, it's only found in any significant quantity on the Rowan Islands.