Which characteristic is typical of quartz?

Quartz is well-known for its ability to occur in a wide range of colors, which results from the presence of impurities, variations in crystal structure, or the effects of light. This characteristic makes quartz an incredibly versatile gem, appearing in hues such as clear (rock crystal), smoky brown (smoky quartz), purple (amethyst), yellow (citrine), and even pink (rose quartz).

The variety of colors increases quartz’s desirability and allows it to be used in various decorative and jewelry applications. This is particularly important within the context of gemology and the study of colored stones, as understanding the different forms and colors of quartz enhances a gemologist's ability to identify and appreciate this abundant mineral.

Other characteristics mentioned, like being soft and easily scratched, highly brittle, or completely opaque, do not accurately reflect quartz as a whole. Quartz is, in fact, considered a relatively hard mineral with a Mohs hardness of 7, making it fairly resistant to scratches. While quartz can be found in opaque forms, it is more commonly transparent or translucent, and the notion of brittleness does not apply to quartz since it generally fractures rather than breaks easily. Thus, the characteristic of forming in a variety of colors distinctly identifies quartz in the realm