Dragon Porcelean

What substances or materials in your world are considered to be purely cosmetic high status or luxury items?
When sand is exposed to extreme heat, it turns into glass. That much is obvious. However, when a high concetration and pressure of acid with Deposits of the mineral Coalint, it creates dragon porcelean- a slick turquise ceramic material, that is incredibly durable from blunt force but is very weak to high volumes, even more than glass. 
When the dragon porcelean does break, it's acidic nature is revelead and it melts all it touches until it dissolves. But the material rarely breaks in day to day activity, so that is of little concern. One popular use for the dragon porcelean is silence rooms- rooms completley made out of the material, where a shout might break a whole wall.
One of the most popular legends about dragon porcelan is about a young poor dwarven miner that wanted to get rich fast. One day he found a lair of an old black dragon, which was trapped and couldn't move. With a piece of mineral he found earlier as a shield he went closer, until the dragon suddenly noticed him and spat acid in his face. 
Surprisingly, the mineral completely protected him. It also quickly turned into a slick ceramic material. The young dwarf saw an oppurtunity, and he started to go there every day with the same mineral. He quickly got rich, and his close friends advised him to stop visiting the dragon. However, the young dwarf couldn't get enought and kept going back for more despite the danger. 
There are two endings to this tale- one is more common outside nohr or in the provinces, the other is the nohrian version. In the common version, the dwarf tried to get a big batch of minerals ready but slipped and got covered by acid. In the nohrian version, the dragon died of old age, and the dwarf only felt sorry for not treating the dragon better.

Type

Ceramic