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No, glass is not a mineral.
Let's go through the elements of the definition of a mineral to see why glass is not considered a mineral:
- Homogeneous: yes
- Naturally occurring: volcanoes and impact craters can produce glass
- Solid: yes (For more on the debate about whether glass is a solid or a liquid, see the Did You Know box back on the main course page)
- Inorganic substance: yes.
- Definable chemical composition: SiO2 *Actually, most industrially-produced glass is not pure silica, but having impurities is still a definable chemical composition so this part of the definition is ok.
- Orderly arrangement of atoms in a lattice: NO. This is why glass is not truly a mineral.
Glass does not have a crystal lattice structure. It is best described as an "amorphous solid" meaning that its atoms are rigidly fixed, but not in an orderly pattern (see the figure below to compare the structure of glass with a crystal lattice structure).
Amorphous structure of a glassy solid (left) and lattice structure of a crystalline solid (right).