Star quartz, often referred to as “star rose quartz” or “asteriated quartz,” is a type of quartz that exhibits a star-like phenomenon known as asterism. This phenomenon occurs due to the presence of tiny rutile needles, or sometimes other inclusions like iron or manganese, within the crystal. When the quartz is cut en cabochon (a method of cutting stones with a convex, polished surface rather than facets), these needle-like inclusions align in such a way that they reflect light in a pattern that appears as a four, six, or even rarely, a twelve-pointed star. The star-effect is best observed under a single light source, when the stone is moved in a circular motion.
Interestingly, since the asterism is dependent on the internal structure of the stone, the orientation of the cut is crucial to bring out the best possible star. The light that causes the star to appear travels along the crystal’s C-axis; the skilled cutting aligns the C-axis perpendicularly to the base of the finished gem to make the star visible when the gem is viewed from above.
Star quartz is a unique example of how certain inclusions, which are often considered imperfections, can actually enhance the beauty and value of a gemstone.
