Spheres

Spheres are the primary currency in most nations on Roshar. Each one consists of a gemstone encased in a glass bead. Gemstones, including the ones in spheres, can temporarily hold Investiture in the form of Stormlight, offering both a source of light and fuel for Surgebindings. Like all gemstones, spheres naturally leak any Stormlight they have absorbed, over a period of about a Rosharan week. This has led to the practice of leaving spheres out during highstorms so they can be recharged. Rosharans use the terms infused and dun to differentiate between spheres that hold Stormlight at the moment, and ones that have gone dark. They were first devised as an alternative to large open flames, as Roshar's atmosphere has a high oxygen content, making flames behave somewhat differently.
== Appearance ==
Kivs seem to be a measurement of gem weight on Roshar. Like other in-world units of measurement, they are not well-defined. Real-life measurements are used here for clarity.	Kivs seem to be a measurement of gem weight on Roshar. Like other in-world units of measurement, they are not well-defined. Real-life measurements are used here for clarity.	Kivs seem to be a measurement of gem weight on Roshar. Like other in-world units of measurement, they are not well-defined. Real-life measurements are used here for clarity.	Kivs seem to be a measurement of gem weight on Roshar. Like other in-world units of measurement, they are not well-defined. Real-life measurements are used here for clarity.
Each sphere is made of a tiny gemstone encased in a glass bead that is usually flattened on one side to keep the sphere from rolling away when set down. The gemstone can belong to any one of the ten Polestones and can come in one of three different sizes. The glass bead is always a uniform size, a little larger than a person's thumb nail.
Exact measurements for the glass beads or their embedded gemstones are not available, but they can be deduced from the known weights of each denomination's gemstone. Spheres gemstones come in three different sizes (see #Currency for more information), so taking the largest one - the one in the broam - allows for some reasonable estimates. The broam gemstone is about 8mm in diameter, assuming a uniform round cut. The distance between the thumb's fingertip and its first joint is about an inch (or 25.4mm), with the nail being roughly half of that, so a nail size of about 12mm is reasonable. Shallan's comment about spheres being slightly larger than a person's thumb nail suggests that spheres are likely in the neighborhood of 15mm to 20mm in diameter.
The table to the left presents the mass and diameter of the gemstone in each denomination, assuming a uniform round cut.
== Light ==
Spherelight colors	Spherelight colors	Spherelight colors
Perhaps the most common use of the spheres is as a light source. Since the gemstones inside them have the ability to hold Stormlight, many Rosharans have adopted the habit of leaving their spheres out during highstorms (in cages or baskets, so they don't get lost or stolen) so they can get (re)charged. Much like the highstorms, Surgebinders are also able to recharge spheres, similarly to how Awakeners can store their Breaths in objects; the Surgebinder must already be Invested, at which point they can will some of their own Stormlight into a gem or sphere. Spheres are leaky containers for Stormlight, however (unlike the perfect gemstones), so they slowly lose their Stormlight to a process similar to evaporation. It takes several days for newly infused spheres to lose all of their Stormlight and become dun, though this amount of time varies slightly with the denomination of the spheres. 
Due to this property of gemstones, infused spheres often serve as a replacement for other, more traditional light sources, such as candles and lanterns. Given that spherelight is both steadier and more consistent, as well as being practically infinitely renewable, it is easy to see how people with access to spheres would consider them superior. The amount of light a sphere gives off varies with the denomination: chips barely have any glow at all, marks glow almost as bright as a candle, and broams glow with the light of several candles. The color of the spherelight also changes predictably from sphere type to sphere type - emeralds glow green, rubies red, and so on. Notably, spherelight from diamonds is considered best for reading, as it is not only closest to natural light, it is also the cheapest gemstone. All spherelight, although reputably steady and calm, is only so in comparison to the even more flickering candlelight; Kaladin observes that the Stormlight inside spheres is actually chaotically shifting, much like a blowing storm.
Although spheres are generally a superior source of light, many people, especially those less well-off or living in poorer regions, still use candles or lanterns. Using candles and lanterns is often cheaper than using spheres, since a sphere's dual status as currency makes it liable to be stolen. This problem does not exist for wealthy or noble lighteyes who may use all-sphere lighting either as a practical matter or to show off their wealth. For example, the entirety of Kharbranth's royal treasury is stored in the Palanaeum to be used as a source of light for the visitors and staff.
The table to the right lists all ten sphere types along with the spherelight color they emit.
== Currency ==
The monetary value of each sphere is a direct consequence of causes both mundane (the size of the sphere's gemstone) and arcane (the Soulcasting properties of each gem type). The gem size defines the denomination of the sphere. From smallest to largest, these are chip, mark, and broam. The gem type is applied as a qualifier to the denomination (e.g. diamond chip, or emerald broam) to form the thirty different monetary units of Roshar. 
One property of Rosharan spheres that does not affect their value is whether they are infused or dun. However, since the glow from the Stormlight is the easiest way to prove that a sphere is not a counterfeit, people are sometimes suspicious of dun spheres and those who try to spend them. Merchants with access to the proper equipment may inspect the gem quality of dun spheres to ensure their authenticity, or call for a moneychanger. Moneychangers serve an additional purpose in Rosharan societies, and that is to offer infused spheres in exchange for dun ones, since an established moneychanger usually has access to secure nests they can safely recharge spheres in. They can extend this service to people interested in recharging their own spheres safely, though this comes with a small convenience fee.
The dominance of spheres throughout Eastern Roshar is slightly weaker in the West. The Tashikki, for example, still use spheres, but instead of carrying them in pouches, they drill holes in the glass beads and keep them on long strings. People even farther west don't even bother with spheres, but use chips of gemstones instead, though they are sometimes encased in hunks of glass.
For details about using spheres as a currency in Shadesmar, see Shadesmar Currency.
=== Value ===
The economic value of each sphere is determined by the type and size of its gemstone.
The gem size defines the three denominations of spheres (chip, mark, and broam), and therefore a fixed exchange rate between the different denominations of spheres of the same type. Within the same gem type, each broam is equivalent to four marks, and each mark is equivalent to five chips - making a broam equal to twenty chips. 
The gem type is a little more complicated. The value of each type of sphere - and, therefore, the relative values of all types - is intrinsically tied to how valuable the given gemstone is in Soulcasting. This makes emeralds -- which can be used to Soulcast grain -- the most expensive kind of spheres, while diamonds are the cheapest. The rest of the sphere types, however, do not all have unique values; instead, they fall within one of three tiers: prime pair, middle weight, and less weight. Combined with the emerald and diamond spheres, this establishes a system with five distinct value tiers. The table below outlines the five tiers, lists the sphere types within each tier, and provides their monetary value expressed in diamond chips, the smallest denomination of the least valued gemstone.
=== Ends ===
Glass spheres that do not contain a gemstone are known as ends. They serve as fake money that can be used to play wagering games such as pieces if the players do not wish to risk real spheres.
== Investiture ==
As useful as spheres are in the everyday life of most Rosharans, their property of holding Investiture in the form of Stormlight is especially useful to a couple of very specific groups of people - Surgebinders and denizens of Shadesmar.
=== Surgebinders ===
For Surgebinders - including both pre-Recreance Knights Radiant and Dalinar's newly restored Orders, as well as wielders of Honorblades such as Szeth prior to his death - the spheres, much like ordinary gemstones, act as a portable, convenient, and inconspicuous source of Stormlight to power their abilities. Because of this, Surgebinders often carry pouches full of infused spheres, although if they find themselves in a situation where their own spheres are unavailable, inaccessible, or dun, they are often able to make use of spheres frequently found in the environment. 
In the days after Kaladin's promotion to a captain in Dalinar's army, Sigzil attempts to establish a baseline for how efficient Kaladin's use of a Full Lashing is by measuring the amount of time it takes for a Lashing powered by the Stormlight from a single diamond chip to run out. The stone remains lashed to the wall for somewhere between 87 and 91 seconds. Sigzil admits, however, that without a clock to track time or a way to quantify variations in how much Stormlight is in a sphere, that the measurements are imprecise. Since arriving in Urithiru, he has continued to attempt precision measurements of Surgebinding, though it is unclear how far he has gotten.
=== Shadesmar Currency ===
Similarly to how spheres have become the dominant currency in the Physical Realm of Roshar, they have become prevalent in its Cognitive Realm as well - though for slightly different reasons. In the Physical Realm the value of each sphere is determined primarily by the economic value of its gemstone, as it relates to Soulcasting. In Shadesmar, however, the real currency is the Stormlight, and spheres become only as valuable as the amount of Stormlight they hold at the moment of the transaction. Presumably out of convenience, prices are still communicated in terms of the sphere denominations defined in the Physical Realm, but the gemstone type becomes irrelevant; a freshly infused diamond mark has the same value in Shadesmar as a freshly infused emerald mark - they are both "one mark of Stormlight," even though in the Physical Realm emeralds are fifty times more expensive than diamonds.
For reasons not yet known, Stormlight fades more quickly in Shadesmar than it does in the Physical Realm, which has led to the development of alternative ways of transporting and transferring Stormlight. The moneychangers in Celebrant, for example, have devices they can use to transfer Stormlight from regular spheres and gemstones into their perfect gems (where it won't fade). In return, they give out notes of exchange, which can be spent like credits within the city's limits. The Rii Oracle possesses a device similar to what the Celebrant moneychangers use, but Captain Ico calls it "foreign technology." 
Neither the full breadth nor depth of the usefulness of Stormlight in Shadesmar is currently known, but it appears to be even more valuable there than it is in the Physical Realm. While it can serve as a regular currency, exchanged for items as mundane as clothes and as exotic as a painting from Nalthis' Court of Gods, it can also help spren change appearance, though perhaps most importantly, it can aid in manifesting souls -- a skill that seems invaluable for the survival in Shadesmar.
== Informal Names ==
Spheres are formally described by their gemstone and denomination. However, in everyday conversations, they are sometimes referred to by color. For example, a ruby mark may be called a "firemark" (and a ruby chip - "firechip"), while a diamond chip may be a "clearchip." Below is the list of known alternate names. Note that the table assumes a common prefix - i.e. while both diamond chips and diamond marks are confirmed to have the clearchip and clearmark shorthand notations, the only confirmed garnet shorthand is the bloodmark; the table simply assumes that a garnet chip would follow a similar naming pattern and be called a bloodchip. It is unknown whether broams get informal names similar to the lesser denominations'. 
== Notes ==
es:Esferas