Tourmalinated Quartz
Tourmalinated quartz, also known as tourmalated quartz or tourmaline quartz is a variety of quartz that has inclusions of tourmaline - typically black (schorl) or colored elbaite tourmaline - growing through or out of it. [1]Another possible variety of tourmaline found in quartz is indicolite (blue) and these have been found in the Sempi Mine in California. [2] Green indicolite quartz has been found in Brazil and can be seen in the first image (below).
Tourmaline (indicolite) Quartz
From Brazil
Photo by Rob Lavinsky, iRocks.com - image lic. under CC-BY-SA-3.0
Sometimes the tourmaline inclusions in tourmalinated quartz are "acicular" (thin needles), either sticking out of the quartz or completely encased in it; somewhat similar in form to those found in rutilated quartz. The tourmaline inclusions typically appear "scattered" in random directions. They may also be thicker 'rods' of tourmaline, and these often appear to be "complete" within the quartz - giving rise to the impression that they "grew right through" the quartz; however, in these instances the tourmaline must have formed first with the quartz forming afterwards.
Schorl is the most common type of tourmaline. It has the chemical formula NaFe3Al6(BO3)3Si6O18(OH)4.
Tourmalinated quartz is very often left unfaceted in order to display its unusual formations. It is also often faceted into a gemstone or made into cabochons, spheres, tumbled stones or other shapes, in order to display the interesting and attractive patterns the tourmaline inclusions can form within a quartz crystal. Tourmalinated quartz cabochons can commonly be seen in jewelry settings such as pendants and rings - where they are often featured with an open back in order to best show the tourmaline inclusions.
Tourmalinated quartz is less common than rutilated quartz, and has been found in Brazil and the USA (in several locations in California, and also in New Hampshire and North Carolina). [3] It is said that it's possible for tourmalinated quartz to be confused with prehnite that has inclusions of black amphibole. [4]
Numerous other minerals may contain tourmaline inclusions: Tourmalinated smoky quartz is also possible - as is tourmalinated amethyst, tourmalinated amazonite, tourmalinated aquamarine, tourmalinated prehnite, tourmalinated peridot and tourmalinated citrine, though some of these are very uncommon indeed: I can see only two examples of tourmalinated peridot currently for sale online, one at 6.21 carats and the other at 8.25 carats.
Tourmalinated quartz appears to have been named relatively recently, and the first appearance of it I can find in literature is from the North Carolina Geological Survey's "Economic Papers" of 1897 [5]
Tourmalinated Quartz Images
Tourmalinated Quartz
From Minas Gerais, Brazil.
Photo by Rob Lavinsky, iRocks.com - image lic. under CC-BY-SA-3.0
Tourmalinated Quartz
From California, USA.
Photo by Rob Lavinsky, iRocks.com - image lic. under CC-BY-SA-3.0
Fonte: CPRM
.jpeg){kind=spacer}
.jpeg){kind=spacer}