6 July 2008
After realizing that I hadn’t been camping for more than a year (yikes!) I immediately jumped on an opportunity to help my undergrad adviser with some fieldwork in the Blue Ridge last weekend. It was great fun to work with all the old hands in the department again, although bushwhacking through tick-infested thornbushes was not my favorite part of the weekend. (Not to mention that making an eight-hour trip up to New York immediately after two days of intense hiking was, to say the least, a bad idea.) Anyway, in examining the basement rocks of the Blue Ridge, we came across a lot of blue quartz. Blue quartz is common in the granites and granitoids out there, and it’s not unusual to come across large veins, most often in the middle of cow pastures. (Cows can be very good at exposing outcrops, but they also do their best to…ahem…cover them up again.)
Blue quartz has been found in Texas, India, Norway, and up and down the East Coast of North America from Rhode Island to South Carolina – mainly in the Blue Ridge. The examples I’ve seen have all been in the Old Rag granite, a Grenvillian-age (900-1600 Ma) coarse-grained granite that crops out often in Shenandoah National Park, and especially at Old Rag Mountain. (For a really good photo of Old Rag granite, look at Callan’s Geology of Shenandoah National Park page.) The Virginia Division of Mineral Resources publishes a quarterly called Virginia Minerals, and the best description I can find of Old Rag blue quartz is in the May 1981 issue. (The online copy is, sadly, in black and white, so it’s impossible to admire the quartz, but a 2002 Virginia Minerals article about the VDMR’s rock garden has a nice color photo.)
Blue quartz is, mineralogically speaking, pretty much like other kinds of quartz, but there are a few significant differences. The Virginia Minerals article says that
The uniqueness of blue quartz is due to properties that are uncharacteristic in ordinary quartz, opalescence, chatoyancy, and asterism. In addition, all blue quartz specimens are highly fractured and contain inclusions of rutile or other minerals.
Blue quartz has an opalescent or “waxy” (according to them) luster, which is changeable (“chatoyant”) depending on the light. Asterism is defined as the “illusion of a star-like figure” in a mineral, and seems to show up in photomicrographs of blue quartz.
There are several things that can cause quartz to look blue. The first is the presence of inclusions that scatter visible light in the blue part of the spectrum – usually zoisite, tourmaline and rutile. The blue color may also come from closely spaced, subparallel microfractures, which are found in all blue quartz samples. Finally, it has been suggested that the presence of titanium (in the form of rutile or ilmenite) could cause the blue color, although there are specimens of blue quartz with no titanium, and quartz of different colors that contains large amounts of titanium.
Here’s the photo from a 2002 Virginia Minerals (from the rock garden in front of their building in Charlottesville):
On the “woo” side of things, blue quartz, apparently, helps balance the lower and higher chakras, brings a sense of order and courage to life, releases fear, and boosts creativity and expression. It also brings mental clarity, helps one see and accept reality, lifts depression, reduces stubbornness and emotional tension, and enhances spiritual development.
Wow, really? Mine must be broken, because my living space is still a mess, I’m stressing about writing a paper and moving to a different state, I have to deal with obnoxious mood swings every month, and I haven’t seen a single indication that I’m less stubborn than I was when I picked up the stuff. Stupid defective minerals. The Old Rag granite owes me a refund. 😉
Wise, Michael A., 1981, Blue Quartz in Virginia: Virginia Minerals, v. 27, no. 2, p. 9-12.
Marr, John and Sites, Roy, 2002, A Guide to the Educational Rock and Mineral Garden: Samples of Virginia’s Geological Diversity: Virginia Minerals, v. 48, no. 2/3, p. 15.