Decide which of the following are not minerals, and explain why: petroleum, wood, coal, steel, concrete and glass.
To be classified as a mineral, a material must possess the following characteristics:
- Natural occurrence: it must occur naturally and hence should not be man-made.
- Crystalline solid substance: should have a well-defined crystalline structure and should be a solid substance.
- Inorganic origin: should not contain carbon.
- Specific chemical composition: should have a defined chemical composition
Using these characteristics, lets check the given options. Steel and concrete are man-made and not natural products and hence cannot be classified as minerals. Coal is a rock and is a combination of minerals and hence cannot be termed a mineral. Petroleum is liquid and hence fails the criteria (of solid phase) for being categorized as a mineral. Most of the glass is industry made and has a composition SiO2 (silica oxide), but does not have a very defined crystalline structure (or arrangement of atoms in the lattice) and hence is not a mineral.
Thus, using the definition of minerals, none of the given options can be termed mineral.
Hope this helps.
I'd add to this that a major reason coal is not considered a mineral is that it is largely composed of carbon (and hydrogen and oxygen), as it is from ancient, compressed plant fossils. One of the definitions of a mineral is that is non-organic, meaning it does not contain carbon.