<p>I will build on <a href="https://anime.stackexchange.com/users/3034/fatalsleep">FatalSleep</a>'s answer:</p>

<blockquote>
  <p><a href="http://kyoukainokanata.wikia.com/wiki/Youmu" rel="nofollow noreferrer">The similarity among all youmu is their tendency to manifest an ore-like stone that contains the powers of that youmu when slain.</a></p>
</blockquote>

<p>In the anime, it is shown that <a href="http://kyoukainokanata.wikia.com/wiki/Sakura_Inami" rel="nofollow noreferrer">Sakura Inami</a> can use Youmu stones to empower "her" spear-like weapon.</p>

<p>Given<br>
<strong>(1)</strong> that the stones have the powers of the youmu and<br>
<strong>(2)</strong> this use of the stones shown on screen,<br>
we can infer that the stones could be used to empower/create magical items.</p>

<p>The barrier sticks, the charms and several other magical artifacts from the Kyoukai no Kanata universe could be made using the power from those stones.</p>

<p>As magical ingredients, youmu stones would be very valuable and highly sought after. This would justify the Ikaishi income, the wealth of some Ikaishi families and the economy of the Youmu stones market.</p>

CC BY-SA 3.0
2014-07-25T14:07:02.970Z
2014-07-27T15:50:19.373Z
2017-04-13T12:54:49.117Z
Mindwin Remember Monica
<p>There isn't really too much source material on the youmu stones besides the anime. However, we see that the youmu stones are brought to appraisers to be sold as a proof of victory over a youmu. However it's never explicitly explained as to what use the stones have.</p>

<p>Based on the Kyoukai no Kanata wiki: <a href="http://kyoukainokanata.wikia.com/wiki/Youmu" rel="nofollow">http://kyoukainokanata.wikia.com/wiki/Youmu</a></p>

<blockquote>
  <p>The similarity among all youmu is their tendency to manifest an ore-like stone that contains the powers of that youmu when slain.</p>
</blockquote>

<p>If this is the case, then the stones could be being used as a medium to create the different powers of all of the Spirit World Warriors. This would explain why stronger youmu that are slain have higher value stones.</p>

CC BY-SA 3.0
2014-07-23T19:21:55.967Z
2014-07-23T19:21:55.967Z
FatalSleep
<p>Youmu stones serve as a proof of victory of Spirit World Warriors over the Youmu. It's unknown what they are useful for except that. Each stone has its own "aura" detectable by Appraisers, who can tell how powerful the defeated Youmu was. Think of the stones as experience points earned in a fighting game. The more you got − the higher level you are, and as a result, thought of as more powerful by other Spirit World Warriors.</p>

CC BY-SA 3.0
2014-07-21T20:32:57.690Z
Yes, if the question was "what are youmu stones" it would be answered, but... XD S2
Mindwin Remember Monica
CC BY-SA 3.0
2014-07-21T20:34:37.973Z
Well, you asked why they are valuable and I answered.
Hakase
CC BY-SA 3.0
2014-07-21T20:43:15.940Z
Ok. This is why they are valuable TO the Ikaishi, but I was asking about their intrinsic value to others. Why the appraisers buy the stones? What they do with it AFTER that?
Mindwin Remember Monica
CC BY-SA 3.0
2014-07-21T20:29:12.243Z
2014-07-21T20:29:12.243Z
Hakase
<p>In Kyoukai no Kanata, the hunters make a living out of selling Youmu stones, allegedly the souls of the defeated youmu. It goes even to the extent of a school teacher taking a leave to hunt during a particular event.</p>

<p>What is the use for those youmu stones after they are sold? Why are they valuable to others?</p>

<hr>

<p>What I am looking for is some source material reference from other media (I only watched the anime).</p>

CC BY-SA 3.0
2014-07-25T14:08:11.470Z
If anyone can bring reference from the Light Novels, they get the green checkmark.
Mindwin Remember Monica
CC BY-SA 3.0
2014-07-28T08:41:42.087Z
"Youmu stones" don't exist in the light novels. They're an anime-only thing.
senshin
CC BY-SA 3.0
2014-07-28T14:34:21.187Z
@senshin that is good to know, even being a turn-off. Fuyukai desu.
Mindwin Remember Monica
<beyond-the-boundary>
What are Youmu Stones used for?
# What are Youmu Stones used for?
Posted by: username_0 on 2014-07-21
In Kyoukai no Kanata, the hunters make a living out of selling Youmu stones, allegedly the souls of the defeated youmu. It goes even to the extent of a school teacher taking a leave to hunt during a particular event.

What is the use for those youmu stones after they are sold? Why are they valuable to others?

---

What I am looking for is some source material reference from other media (I only watched the anime).
**Tags:** beyond-the-boundary
> **Comments:**
> **username_0**: If anyone can bring reference from the Light Novels, they get the green checkmark.  
> **username_1**: "Youmu stones" don't exist in the light novels. They're an anime-only thing.  
> **username_0**: @senshin that is good to know, even being a turn-off. Fuyukai desu.  
---
## 3 answers
### Answer by username_0 on 2014-07-25. Score: 4
I will build on [FatalSleep](https://anime.stackexchange.com/users/3034/fatalsleep)'s answer:

> [The similarity among all youmu is their tendency to manifest an ore-like stone that contains the powers of that youmu when slain.](http://kyoukainokanata.wikia.com/wiki/Youmu)

In the anime, it is shown that [Sakura Inami](http://kyoukainokanata.wikia.com/wiki/Sakura_Inami) can use Youmu stones to empower "her" spear-like weapon.

Given  
**(1)** that the stones have the powers of the youmu and  
**(2)** this use of the stones shown on screen,  
we can infer that the stones could be used to empower/create magical items.

The barrier sticks, the charms and several other magical artifacts from the Kyoukai no Kanata universe could be made using the power from those stones.

As magical ingredients, youmu stones would be very valuable and highly sought after. This would justify the Ikaishi income, the wealth of some Ikaishi families and the economy of the Youmu stones market.
---
### Answer by username_2 on 2014-07-23. Score: 3
There isn't really too much source material on the youmu stones besides the anime. However, we see that the youmu stones are brought to appraisers to be sold as a proof of victory over a youmu. However it's never explicitly explained as to what use the stones have.

Based on the Kyoukai no Kanata wiki: <http://kyoukainokanata.wikia.com/wiki/Youmu>

> The similarity among all youmu is their tendency to manifest an ore-like stone that contains the powers of that youmu when slain.

If this is the case, then the stones could be being used as a medium to create the different powers of all of the Spirit World Warriors. This would explain why stronger youmu that are slain have higher value stones.
---
### Answer by username_3 on 2014-07-21. Score: 1
Youmu stones serve as a proof of victory of Spirit World Warriors over the Youmu. It's unknown what they are useful for except that. Each stone has its own "aura" detectable by Appraisers, who can tell how powerful the defeated Youmu was. Think of the stones as experience points earned in a fighting game. The more you got − the higher level you are, and as a result, thought of as more powerful by other Spirit World Warriors.
> **Comments:**
> **username_0** (2014-07-21): Yes, if the question was "what are youmu stones" it would be answered, but... XD S2  
> **username_3** (2014-07-21): Well, you asked why they are valuable and I answered.  
> **username_0** (2014-07-21): Ok. This is why they are valuable TO the Ikaishi, but I was asking about their intrinsic value to others. Why the appraisers buy the stones? What they do with it AFTER that?  
---
