Smoky Quartz stands above the others.

Smoky Quartz: In a Class of Its Own
Smoky quartz may seem like any other variety of quarts at first, but it does posses characteristics that differentiate it from other specimens. For one, the color of the stone itself can range from a deep brown to a true black-few other gemstones out there have this distinction. Smoky quartz has had a lot of radiation in the midst of formation (which does not remain in the stone) the colors allow for a wide variety. It is important to note that some smoky quartz out on the market has been artificially irradiated to produce a deeper black color.
Both the Sagittarius and Capricorn astrological signs are associated with smoky quartz. Ambitious, practical and methodical are traits often used to describe a person with the Zociac sign of Capricorn. Sagittarians are known to be easy-going, positive, and normally jovial. Smoky quartz has several traditional traits that will come to people wearing these stones often.
Among other things, smoky quartz can root the person wearing it and allow for group cooperation. This stone will help control reckless behavior and transform negative feelings of anger into calmness and develop a protection around from negative feelings and thoughts.
The smoky quartz gemstone is also known for it's ability of healing feet, hands, and back problems. It calms the nerves while promoting healing to said areas and alleviates pain in the said areas.

Smoky Quartz always looks good.