Rutilated Quartz (black)

"Black rutilated quartz" is a trade name for natural quartz containing dark, black-looking needles. Rutile itself can be greyish-black to black, but black needles in quartz are often tourmaline: a Chinese study found that the inclusions in market "black hair crystal" (黑髮晶) were mostly black tourmaline. A piece sold under this name may therefore contain rutile or tourmaline, and only testing of the inclusion can tell which.