The relatively abundant mineral smoky quartz ranges in color from almost black to nearly colorless. Gem quality specimens are mined from the Swiss Alps and from Pike's Peak in Colorado. Dark smoky quartz is sometimes heat-treated to give it a lighter color which appears more brilliant when cut.
Tourmaline is a coveted stone that comes in a wide range of colors from black to pink, green and blue. Crystals which display more than one color together are common. A cross-section of a watermelon tourmaline crystal reveals green on the outside and pink within.