Inclusions in quartz are not uncommon and there are literally hundreds of different varieties of included quartz. Whilst many stones lose value if they are included quartz in many cases does exactly the opposite and are prized specifically for their inclusions. Inclusions in quartz can be air, water, tar, petroleum or any number of other minerals however rutile is one of the most common. Rutile is best known for its needle-like crystals which are often found in other minerals but particularly in quartz and corundum. The mineral rutile which is made up primarily of titanium dioxide grows naturally within the stone over millions of years. Its long slender crystals resemble fine strands of golden hair hence are sometimes referred to as Venus hair or Cupid's darts. Although very occasionally referred to as sagenite, quartz included with rutile is more commonly known as rutilated quartz.
Rutilated quartz is used primarily as a gemstone and although it may be polished as a cabochon, finer grade stones tend to be faceted. The density of the inclusions can vary dramatically from one stone to the next and crystals may be relatively thick or exceptionally fine. Their colour can also vary from pale gold to a rich orangey brown and whilst some stones may feature just a handful of golden hair-like strands, others can be full to capacity to the point where the quartz no longer exhibits translucency.
When inclusions of rutile are present in the mineral corundum specifically rubies and sapphires, if particularly dense they can cause a visual phenomenon known as asterism. This is caused as light reflects off of the rutile but the phenomenon can only be seen when the stone has been expertly cut as a cabochon. Where asterism is present stones become known either as star ruby or star sapphire due to the fact that a star-like reflection can be seen.
Another relatively common inclusion in quartz is the mineral tourmaline but stones are sometimes referred to as black rutile or rutilated quartz both of which are incorrect because the mineral inclusion is tourmaline not rutile. The correct name for this variety of included quartz is tourmalinated quartz.
Other varieties of included quartz include aventurine which features with the mineral mica and lodolite which is particularly rare variety that can only be found in the Minas Gerais region of Brazil. Lodolite often features complex patterns of sand-like crystals that often resemble coral reefs, gardens or landscapes hence it may also be referred to as Garden, Landscape or Scenic Quartz.