Select the one substance that is not a rock.

 - Diorite is formed in nature. It is a solid.
 - Quartzite is formed in nature. It is a solid.
 - Ceramic is made in a factory. It is a solid.
Compare the properties of each substance to the properties of rocks. Select the substance whose properties do not match those of rocks.
Diorite is a rock.
Ceramic is made in a factory. But all rocks are formed in nature.
So, ceramic is not a rock.
Quartzite is a rock.