Rockhounds and lapidaries often use the term "sagenite" or sagenitic quartz, to describe all types of included macrocrystalline quartz, especially those specimens that include rutile crystals. Probably the most well known and easiest to identify, rutilated quartz is when clear through semi-clear quartz contains slender needles of embedded titanium dioxide crystals. The rutile needles can appear to be in the shape of an open fan or radiating mass, known as acicular, or they can look like individual floating pieces of hair frozen forever in space. Those of us familiar with paints know that pure titanium dioxide is an important pigment used to produce a brilliant white, however due to trace amounts of other minerals, rutile crystals can be silver, red, reddish-brown, gold or yellow. When rutiles in a crystal appear to be more heavily concentrated at the bottom of the crystal than at its point, more than likely the titanium dioxide crystals formed first and then the quartz filled in around them, perfectly preserving the structure of the rutiles. Faceted stones or cabochons that visibly show rutile crystals in a star-like formation are rare and most desirable. Some of the other names for rutilated quartz include Venus Hair Stone and either Hair or Needle stone. Most of the rutilated quartz today is mined in either Brazil or South Africa.
Pictured: Although not a perfect example, this faceted rutilated quartz shows a "star" formation and Dale's personal collection of beautiful, rutilated quartz stones in many colors and Gold rutilated quartz made into a classic cabochon ring design by Dale "Cougar" Armstrong.