Inclusions in Quartz are Extremely Common
Also Known as Included Quartz
Inclusions in quartz are relatively common and there are hundreds of different varieties.
When inclusions are present in a mineral or a gemstone it often leads to a decrease in value. In others the value can increase because of certain inclusions.
Inclusions in quartz can be air water tar petroleum or any number of other substances. The minerals rutile and tourmaline are particularly common.
Rutilated quartz and tourmalinated quartz are two of the best known varieties of included quartz. Rutile is known for its long and slender needle-like crystals which are made up primarily of titanium dioxide.
These grow naturally within the quartz over millions of years and often resemble fine strands of hair. For this reason they're sometimes known as Venus hair or Cupid's darts.
Rutilated quartz is also known as sagenite although this name is now rarely used.
Golden rutile tends to be the variety most people are familiar with. The of rutile however can vary from pale yellow to a rich orange or reddish brown and can even be black. Black rutile inclusions can sometimes be mistaken for tourmaline. Quartz with included with tourmaline is correctly known as tourmalinated quartz.
Rutilated and tourmalinated quartz are both widely used for gemstones. Stones tend shaped as cabochons.
The density of the inclusions can vary dramatically. Whilst some stones may only be very lightly included, others can be full to capacity. When heavily included the quartz can look almost opaque.
When rubies and sapphires are densely included with rutile, an optical phenomenon known as asterism can often be seen. This is caused as light reflects off the fine rutile crystals. For it to be fully appreciated the stone must be shaped as as a cabochon.
Where asterism is present the gemstone becomes known as star ruby or star sapphire. This is because a star-like reflection can be seen.
Another variety of included quartz is aventurine. This stone features inclusions of mica.
The rutilated quartz in our first photo is on display in the Smithsonian Museum of Natural History, Washington D.C. Photo by Stone Mania. The photo is clickable and redirects to the original non-compressed image.