Currency on Roshar is based on spheres; little glass beads embedded with gemstones of various sizes. The glass portion of most spheres are the same size; the size of the gemstone at the center of each determines its denomination.
Spheres are glass beads, a little larger than a person's thumbnail with a much smaller gemstone set within its center. The gemstones are able to absorb Stormlight, which makes the spheres glow. Most spheres are also flattened on one side, to keep them from rolling away when set down.
Spheres are a practical currency. The gemstones within them absorb Stormlight infused during highstorms and they will stay infused for about a week. The Stormlight within them causes the spheres to glow, turning them into a cheap, rechargeable, mobile light source commonly used for illumination everywhere. Such infused Stormlight is also used to power various fabrials.
The size of a gemstone and its type greatly influence its value; the larger the stone, the more Stormlight it can gather and the more powerful its effects will be. Different types of fabrials require different types of gemstones. For example, emeralds are most valuable, since they can be used by Soulcasters to create food. (Kaladin noted that the emerald broam he found while on chasm duty was the highest denomination.)
Stormlight can be measured in chips; gemstones are precisely weighed before being encased in glass. Uncut gems hold less Stormlight than cut gems. Also, Stormlight fades from a sphere over time.
Spheres which run out of Stormlight are called dun spheres. Infused spheres are not worth any more than dun spheres, though sometimes dun spheres are suspect because it is more difficult to see the gemstone inside them, and sometimes a moneylender would have to be brought in to judge the authenticity of a gemstone.
The size of a gemstone inside a sphere determines its denomination. Gemstones come in three denominations: chips, marks and broams. There are five chips to a mark, and four marks to a broam.
|Broam||Equal to four marks, or twenty chips.||Provides the light of several candles.|
|Mark||Equal to five chips.||Provides a little less light than a candle.|
|Chip||One chip.||Provides visible light far fainter than a lamp.|
Nine of the ten Polestones are used for currency. It is not known whether the ninth is smokestone or heliodor, but the others are confirmed currency gemstones. Clearmarks refer to diamond marks.
The relative values of some gems are unknown, but it is certain that emeralds are worth the most, and diamonds the least, both due to their relative use in Soulcasting; emeralds are used to make food, while diamonds are used to make crystal, glass, and quartz.
|Diamond||clear||1 diamond chip||5 diamond chips||20 diamond chips|
|Garnet||blood||5 diamond chips||25 diamond chips||100 diamond chips|
|Ruby||fire||10 diamond chips||50 diamond chips||200 diamond chips|
|Sapphire||sky||25 diamond chips||125 diamond chips||500 diamond chips|
|Emerald||50 diamond chips||250 diamond chips||1000 diamond chips|
The values of Smokestone, Amethyst, Topaz, Zircon and Heliodor are yet unknown.