Quartz is one of the most important minerals on earth and makes up one of the most popular gemstone groups in the world of colored stones. Quartz gemstones are very attractive, durable and hard. Some quartz varieties can be extremely rare, while others are very readily available.The color of macrocrystalline quartz is as variable as the spectrum, but clear quartz is by far the most common color followed by white or cloudy quartz. Purple (amethyst), pink (rose quartz), gray or brown to black (smoky quartz) are also common. Cryptocrystalline quartz varieties can be multicolored. In artificial light, quartz does not display a desirable quality. It looks best in daylight, particularly after sunrise and just before sunset.Fine quartz is transparent, which means that the light passes through the stone unhindered. In translucent quartz, the passage of light through the stone is slightly weakened. The best quality quartz is "clean", free from inclusions of any kind.