Stormlight is a glowing substance brought by the Highstorms like an energy source.
Gemstones whether bare or encased in glass spheres, left outside during a highstorm will become infused with Stormlight, which will remain within the stones for a week or so, the Stormlight can then be used to fuel the operation of fabrials and lamps or used to fuel Surgebinding abilities. When held by a Surgebinder or leaking from damaged Shardplate, Stormlight appears as a luminescent white vapor.