Polestone

The Polestones are the ten varieties of gemstone that naturally hold Light. They also serve as the basis of spheres, the basic Rosharan money system.
== Attributes ==
=== Composition ===
Some Polestones are the same type of crystal but with different color and chemical signatures. Sapphire and ruby are both types of corundum. Smokestone and amethyst are both types of quartz. Emerald and heliodor are both types of beryl. Much like how iron and steel, despite being very similar chemically, are different metals in the Metallic Arts, the exact color and chemical signatures are enough to differentiate the Polestones. As a result, an off-color Polestone acts much like an impure alloy in Allomancy. If a Polestone was drained of its color by an Awakener, it would still hold Stormlight but would have the properties of a dusty or cloudy quartz. If a spren was trapped inside, they would be released.
If sung to, while holding Light, Polestones will break.
=== Light and Surgebinding ===
All Lights can be stored in gems. How long a given quantity of Light will remain in a specific gem depends on the type of Light and the quality of the gem. The rate at which a Light leaks from gemstones is not constant either - it appears slow at first, but accelerates rapidly near the end, making gems that begin to dim, dim fast. Regardless of the type of Light, perfect gems are said to be able to hold it indefinitely, but they are extremely rare.
Although the type of Polestone Stormlight is stored in is irrelevant for most Surgebinding, Polestones do have an important impact on Soulcasting. Namely, they determine what kind of substances a Soulcaster can transmute objects into. It is believed to be impossible to create Polestones via Soulcasting.
=== Spren ===
In addition to the ability to hold Stormlight, Polestones are able to trap spren. The type of spren that can be trapped depends on the Polestone used and its cut. This quality serves as the basis for fabrials. Each Polestone is associated with one of the Ten Essences and with an Order of Knights Radiant. However, there appears to be no functional difference between Polestones apart from Soulcasting and fabrial creation.
If a Polestone is set in the pommel of a deceased Shardblade it allows the blade to be bonded, whereby it can be summoned and dismissed. Synthetic versions of the Polestones could also be used in fabrials.
== The Ten Polestones ==
=== Sapphire ===
Sapphire is associated with the Essence of Zephyr. They are used to Soulcast translucent gases, like air.
Sapphire spheres are given the "sky-" prefix.
It is associated with the Order of Windrunners
=== Smokestone ===
Smokestone is associated with the Essence of Vapor. They are used to Soulcast opaque gases, like smoke and fog. 
Smokestones are used in a type of fabrial clock.
It is associated with the Order of Skybreakers.
Smokestone is a chemically impure version of quartz.
=== Ruby ===
Ruby is associated with the Essence of Spark. They are used to Soulcast fire.
Rubies are used in the production of conjoiner fabrials, where a single infused ruby is split in two. Once activated the two halves will mirror each others movements, lift one and the other will also rise. Spanreeds are a common application of this phenomenon.
Rubies are also used in a kind of heat producing fabrial. They are also used in the construction of a painrial, a pain reducing fabrial, designed by Longshadow and adapted by Navani Kholin. A ruby was also part of the Oathgate at the center of the Shattered Plains.
Ruby spheres are given the "fire-" prefix.
It is associated with the Order of Dustbringers
=== Diamond ===
Diamond is associated with the Essence of Lucentia. They are used to Soulcast crystals, like quartz and glass.
Diamonds are used in a kind of light producing fabrial.
Diamond spheres are given the "clear-" prefix.
It is associated with the Order of Edgedancers
=== Emerald ===
Emerald is associated with the Essence of Pulp. They are used to Soulcast plant material, like wood, moss, and grain.
Emeralds can be used to capture flamespren. They can be found in chasmfiends.
It is associated with the Order of Truthwatchers
=== Garnet ===
Garnet is associated with the Essence of Blood. They are used to Soulcast the eight types of blood and all other non-oil liquids.
Garnets are used in a type of water attracting fabrial.
Garnet spheres are given the "blood-" prefix.
It is associated with the Order of Lightweavers
=== Zircon ===
Zircon is associated with the Essence of Tallow. They are used to Soulcast oils.
It is associated with the Order of Elsecallers
=== Amethyst ===
Amethyst is associated with the Essence of Foil. They are used to Soulcast metals.
Amethysts are used in the production of reverser fabrials, where a single infused amethyst is split in two. Once activated the two halves will inversely mirror each other's movements, lift one and the other will be lowered.
It is associated with the Order of Willshapers
=== Topaz ===
Topaz is associated with the Essence of Talus. They are used to Soulcast rock and stone.
A topaz was observed as part of a fabrial replicating Regrowth, an application of the Surge of Progression.
It is associated with the Order of Stonewards
=== Heliodor ===
Heliodor is associated with the Essence of Sinew. They are used to Soulcast animal material, like meat and flesh.
Heliodors are used in the production of alerter fabrials. These fabrials can be used to detect a variety of stimuli, such as people and emotions, and give notice to its user. The larger the heliodor, and as a result the more Stormlight that can be infused in it, the wider the fabrial's range is.
A heliodor was observed as part of a fabrial replicating Regrowth, an application of the Surge of Progression.
It is associated with the Order of Bondsmiths
They can be found in gumfrems.
A perfect heliodor was used to imprison Ba-Ado-Mishram.
== Obtaining ==
While Polestones are produced via mining, a significant source of them on Roshar is the harvesting of the gemhearts that grow inside greatshells. Larger species of greatshell, like chasmfiends, produce gemhearts of great size, which are incredibly useful in Soulcasting as a larger stone is less likely to break from the strain. This trait however has led to many species of greatshells, such as the lanceryn, to go extinct. The exact method by which gemhearts are grown is not understood, though it is known to be caused by a leak from the Spiritual Realm into the Physical, and is analogous, though not identical, to the production of atium in the Pits of Hathsin on Scadrial. Although they may have flaws, gemheart Polestones have virtually no impurities, unlike their conventionally mined counterparts.
== Perfect Gemstones ==
Perfect gemstones occur when one of the Polestones forms without any flaws or imperfections which allows them to hold light indefinitely. The money exchangers living in major cities of Shadesmar use perfect stones to store the Stormlight they use for currency. The King's Drop is a perfect gemstone that has been held in the Thaylen Gemstone Reserve for over two hundred years without being renewed or losing Stormlight. In addition to not leaking, a perfect gemstone can hold far more Stormlight than a normal gemstone of the same size could. The Elsecallers were tasked with protecting perfect gems, including a ruby named Honor's Drop. The honorspren have gathered many perfect gemstones in their stronghold Lasting Integrity. Jasnah Kholin believes that there are far fewer perfect gemstones around in the Physical Realm than there should be, suggesting that someone may have been gathering them up before their value was more widely known; possibly the Ghostbloods as they are experimenting with transporting Stormlight off-world.
Perfect gemstones have the capacity to hold Cognitive Shadows in addition to spren, the latter of which they have a far larger capacity than normal gemstones--they can hold Heralds, the Unmade, and even Fused. They could also capture some of the Dor or the sunlight from Taldain.
== Transfer ==
It is possible to transfer Light from a filled, small gemstone to a large and empty gemstone of its type by holding the filled gemstone to the empty one. This method of transfer is slow and inefficient; however, the Thaylens have discovered a more efficient way of transferring Stormlight from one gemstone to another. By using a tuning fork of a specific frequency, a person can touch an infused gemstone and then touch the fork to the empty gemstone for a rapid mode of transfer. With the Thaylen method, the type of Polestone does not matter, and light can be transferred from any type to any type. The decay rate is unknown, as is the distance the tuning fork can be brought before transfer is impossible.
Surgebinders are also able to infuse Polestones regardless of the type, and can do so very quickly.
== Roshar Economy ==
Gemstones form the basis for the Roshar economy. Gemstone weight is measured in kivs. When used as currency, the gems are encased in glass spheres. Although the spheres are of uniform size, the gemstones inside are of three sizes. In descending order of size (and value), these gem sizes are broam, mark, and chip.
In addition, the value of the “sphere” is determined by the type of gemstone, which have different values as determined by their utility rather than their rarity.. Their relative value in descending order is as follows: emerald, sapphire, ruby, diamond, and garnet. In addition, amethyst is one of the more valuable gemstones; topaz and zircon are amongst the least valuable.
== Notes ==
;Footnotes
; References
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