What is the usage of the stones monsters drop?


According to the [Wiki page](https://dungeon-ni-deai-o-
motomeru.wikia.com/wiki/Items), adventurers can exchange the gems they collect
in the dungeon for money.

> Magic stones are crystal-like stones that are dropped by monsters. The
> stones can be exchanged at the Guild for valis (Orario currency).
>
> The bigger the stone, the more valis it is worth.

I was wondering, why does the Guild want these crystals? Do they have a use?

![Gem](https://i.stack.imgur.com/ylUic.png)




According to
[ja.Wikipedia](http://ja.wikipedia.org/wiki/%E3%83%80%E3%83%B3%E3%82%B8%E3%83%A7%E3%83%B3%E3%81%AB%E5%87%BA%E4%BC%9A%E3%81%84%E3%82%92%E6%B1%82%E3%82%81%E3%82%8B%E3%81%AE%E3%81%AF%E9%96%93%E9%81%95%E3%81%A3%E3%81%A6%E3%81%84%E3%82%8B%E3%81%A0%E3%82%8D%E3%81%86%E3%81%8B#.E3.82.A2.E3.82.A4.E3.83.86.E3.83.A0.E9.96.A2.E9.80.A3):

> **魔石**
>
> モンスターの生命力の核にして、冒険者の飯の種。例外なく胸部に存在する。  
>  モンスターを倒して胸の魔石をえぐり出し（アニメでは倒すと肉体が消失して魔石だけが残る）、ギルドで換金するのが冒険者の主な収入源。  
>  魔力が込められており、照明や下水浄化、調理用コンロ、冷蔵庫など、さまざまな道具に用いられる。  
>  胸の魔石を直接攻撃して砕いた場合、モンスターは即死する。

> Magic Stones are the core of the monsters' life force, and adventurers'
> means of living. Without exception, it locates in the monster's chest.
>
> Killing the monsters, gouging the Magic Stones out of their chests (in the
> anime, the body of the monsters disappear when defeated, leaving their Magic
> Stones behind), and cashing them in at the guild is **the main source of
> income of the adventurers**.
>
> Charged with magic, **Magic Stones can be used to create various tools** ,
> such as lighting, sewage purification, cooking stove, refrigerator, etc.
>
> Monsters die an instant death if the Magic Stone in their chest is destroyed
> by a direct attack.

[DanMachi Wiki](http://dungeon-ni-deai-o-motomeru.wikia.com/wiki/Magic_Stone)
has a bit more details regarding the use of Magic Stones:

> ## Uses
>
>   * **Magic Stone Lamp:** A handy and flexible use of the Magic Stone is the
> production of Magic Stone Lamps. These items give off a dim shine that
> allows one to see underground or in total darkness. It was once considered
> as the "century's greatest invention."
>   * **Ignition Device:** Magic Stones can be used to produce ignition
> devices.
>   * **Freezer:** Magic Stones are used in the production of freezers to
> preserve food.
>

Volume 1, Chapter 2 is cited as the source of the information above.




According to
[ja.Wikipedia](http://ja.wikipedia.org/wiki/%E3%83%80%E3%83%B3%E3%82%B8%E3%83%A7%E3%83%B3%E3%81%AB%E5%87%BA%E4%BC%9A%E3%81%84%E3%82%92%E6%B1%82%E3%82%81%E3%82%8B%E3%81%AE%E3%81%AF%E9%96%93%E9%81%95%E3%81%A3%E3%81%A6%E3%81%84%E3%82%8B%E3%81%A0%E3%82%8D%E3%81%86%E3%81%8B#.E3.82.A2.E3.82.A4.E3.83.86.E3.83.A0.E9.96.A2.E9.80.A3):

> **魔石**
>
> モンスターの生命力の核にして、冒険者の飯の種。例外なく胸部に存在する。  
>  モンスターを倒して胸の魔石をえぐり出し（アニメでは倒すと肉体が消失して魔石だけが残る）、ギルドで換金するのが冒険者の主な収入源。  
>  魔力が込められており、照明や下水浄化、調理用コンロ、冷蔵庫など、さまざまな道具に用いられる。  
>  胸の魔石を直接攻撃して砕いた場合、モンスターは即死する。

> Magic Stones are the core of the monsters' life force, and adventurers'
> means of living. Without exception, it locates in the monster's chest.
>
> Killing the monsters, gouging the Magic Stones out of their chests (in the
> anime, the body of the monsters disappear when defeated, leaving their Magic
> Stones behind), and cashing them in at the guild is **the main source of
> income of the adventurers**.
>
> Charged with magic, **Magic Stones can be used to create various tools** ,
> such as lighting, sewage purification, cooking stove, refrigerator, etc.
>
> Monsters die an instant death if the Magic Stone in their chest is destroyed
> by a direct attack.

[DanMachi Wiki](http://dungeon-ni-deai-o-motomeru.wikia.com/wiki/Magic_Stone)
has a bit more details regarding the use of Magic Stones:

> ## Uses
>
>   * **Magic Stone Lamp:** A handy and flexible use of the Magic Stone is the
> production of Magic Stone Lamps. These items give off a dim shine that
> allows one to see underground or in total darkness. It was once considered
> as the "century's greatest invention."
>   * **Ignition Device:** Magic Stones can be used to produce ignition
> devices.
>   * **Freezer:** Magic Stones are used in the production of freezers to
> preserve food.
>

Volume 1, Chapter 2 is cited as the source of the information above.

