Among the quartz that form crystals, one can name citrine, morion, rauchtopaz, amethyst, rock crystal. Interestingly, the colors in this group of quartz are unstable, and one type of quartz is easily transformed into another by heating or irradiation - amethyst and morion into citrine, amethyst into green prasiolite, and each of the quartz that has a color into rock crystal, since when heated up to a certain temperature, they completely lose their color.
It is also necessary to note another group of crystalline quartz - "hairy" quartz. "Hairs" are crystals of rock crystal (clear quartz) with needle-like inclusions of rutile ("Venus hair") or tourmaline ("Cupid's arrows"). Here one should be careful in the name of the corresponding stone, since rock crystal with rutile inclusions is often called rutile quartz, simply shortened to "rutile", which is incorrect, since rutile is only one of the parts that make up rutile quartz. Moreover, the short, but categorically incorrect designation "rutile" can also refer to quartz with inclusions of black tourmaline (the so-called "black hairy").