Final answer:
Sugar (sucrose) is not classified as a mineral because, although it is a solid with a definite chemical composition and crystalline structure, it is an organic compound, not inorganic.
Step-by-step explanation:
The substance in question is sugar. To classify sugar as a mineral or not a mineral, we must refer to the definition of a mineral. A mineral is defined as a naturally occurring, inorganic solid with a definite chemical composition and a characteristic crystalline structure.
Sugar, or sucrose, is certainly a solid with a definite chemical composition (C12H22O11), and it has a crystalline structure. However, it does not fit the criteria of a mineral because it is not inorganic; sugar is an organic compound because it contains carbon atoms bonded to hydrogen atoms and is derived from plants or animals. Therefore, sugar is not classified as a mineral.