Select the one substance that is not a rock.

 - Syenite is a solid. It is not a pure substance.
 - Phyllite is not a pure substance. It is a solid.
 - Burlap 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.
Syenite is a rock.
Burlap is made in a factory. But all rocks are formed in nature.
So, burlap is not a rock.
Phyllite is a rock.