Tourmalinated Quartz

The photo shows three polished stones, translucent and greyish, with black lines inside. The large stone is packed with thin needles crossing in every direction, and the two small ones have fewer needles, but thicker. According to Fire Mountain Gems, tourmalinated quartz is clear quartz that grew together with black tourmaline, hence the name. And according to Minerals.net, black tourmaline, called schorl, can grow as tiny dense needles inside a quartz crystal.

How do needles get inside a stone? According to Geology Science, it happens mainly in pegmatites, rocks where minerals crystallize slowly and large. The tourmaline crystallizes, the quartz grows around it, and in the end it closes over it from every side. The result is like a frozen snapshot of two minerals mid-growth. And according to the site, the direction and density of the needles vary from stone to stone, so each one has its own pattern.

It is easy to confuse with rutilated quartz, which has needles too. According to Fire Mountain Gems, the difference is the color: in rutilated quartz the needles are golden or silvery, and in tourmalinated quartz they are black. Ours are completely black, so everything checks out.

This stone also has an electric side, twice over. According to Fire Mountain Gems, quartz is piezoelectric, meaning it builds up an electric charge when squeezed, which is why it is used in watches. And according to Minerals.net, black tourmaline is piezoelectric too, and it becomes strongly charged when heated as well. Two electric minerals in one stone, and you still cannot charge a phone with it.

According to Fire Mountain Gems, most tourmalinated quartz for jewelry comes from Brazil. Its hardness, according to Geology Science, is 7, like all quartz, and according to the site, the needles hardly change it. And according to Fire Mountain Gems, it usually needs no treatment, although it is sometimes dyed.