October 3, 2011

Geology Word of the Week: R is for Rutile

Posted by Evelyn Mervine

Thin, needle-like crystals of rutile in quartz. Photo courtesy of Dana Hunter.

def. Rutile:
A high-pressure, high-temperature mineral that is the most common form of titanium oxide (TiO2). Rutile is commonly found in metamorphic rocks, such as eclogite. Rutile is also found as an accessory mineral in igneous rocks, particularly in deeper-formed plutonic igneous rocks and also volcanic rocks with deep sources, such as kimberlites. Rutile is an important economic mineral that is mined for titanium. Rutile often forms as thin, needle-like crystals, which are commonly found as inclusions in minerals such as quartz and corundum. Rutile is commonly a brownish-red color due to the presence of iron impurities. Reflecting this characteristic color, the name rutile derives from the Latin word “rutilus,” which means “red.”

Rutile is often found in metamorphic rocks. For example, here are some thin section images showing rutile (red-colored mineral) in an ultra-high-temperature granulite:

Rutile in thin section in UHT granulite. Photo courtesy of Tanya Ewing.

Rutile in thin section in UHT granulite. Photo courtesy of Tanya Ewing.

Rutile is also found as an accessory mineral in some igneous rocks.  Most igneous rutiles are fairly small.  However, when space and time permit, large igneous rutile crystals may form in pegmatites. For example, here’s a gigantic crystal of rutile that likely formed as a pegmatite mineral:

That's quite the rutile crystal! Photo courtesy of Paul Glasser.

Rutile can also be found as a secondary mineral in hydrothermal veins. Hydrothermal veins form when heated fluids circulate through a rock, picking up certain elements and concentrating them elsewhere. For example, gold is often concentrated through hydrothermal circulation. Since silica is a major component of many rocks, quartz is a very common hydrothermal mineral and can often be found as secondary veins in rocks which have experienced hydrothermal alteration. Hydrothermal minerals such as quartz are often deposited in cracks or spaces (such as vesicles or vugs) in a host rock. Sometimes, quartz contains thin, needle-like crystals of rutile. When this occurs, the quartz is named “rutile quartz” or “rutilated quartz.”  The long rutile crystals found in rutilated quartz generally form in a cavity, such as a vug– a place where they have space to grow into long needles. Then, these rutile needles are incorporated into hydrothermally-deposited quartz. Some rutile inclusions in quartz may also form as a result of metamorphism, but most rutilated quartz forms through hydrothermal processes*.

Gemstones which contain inclusions are generally considered less-valuable than inclusion-free gemstones. However, rutile inclusions are desired in certain gemstones. For example, rutile inclusions make for some gorgeous quartz crystals (see pictures above and below). Rutile inclusions in corundum and other minerals are responsible for asterism, an optical phenomenon that creates “star gems” such as star sapphires.

Closer view of Dana's rutilated quartz. Photo courtesy of Dana Hunter.

As I discovered this evening when I was googleing rutilated quartz, there are many woo-woo pseudoscientific “properties” associated with rutilated quartz. In my google search, I was hoping to learn about the geologic properties of rutilated quartz. Unfortunately, many of the websites I found on google informed me about some other “properties” of rutilated quartz. For instance, one of these websites “informed me” that rutilated quartz:

Brings forth each person’s strengths, originality, aids sleep, relate to others.

Rutile is said to intensify the metaphysical properties of its host crystal and to enhance one’s understanding of difficult situations. It is also said to enhance creativity and to relieve depression and loneliness.

Rutilated quartz is said to slow down the aging process and is said to be a strong healer.

Source of the above quotation.

Well, I’m no doctor, but I have a feeling that placing rutilated quartz around my house is not going to help me sleep (I’ve had insomnia for years, and I mange it fine without woo-woo crystals) or prevent wrinkles. I suppose that placing rutilated quartz all over my house could help relieve depression. I do love pretty crystals.

My friend Dana Hunter agrees that the woo-woo properties of rutilated quartz are nonsense. When she sent me the two beautiful pictures of her piece of rutilated quartz, she also sent this delightful story:

I know you sometimes like to laugh at woo in these Word of the Week posts, and there’s definitely woo involved with rutilated quartz. This little piece was purchased at a crystal shop in Sedona, AZ, back when I was a wooful middleschooler. What you did was tie a string round its middle, dangle it like a pendulum, and ask it yes-or-no questions. It would swing in a circle or from side-to-side to answer (you had to ask first “What is yes?” and “What is no?” to determine which was which). Supposedly, then, it could predict the future. Freaky, watching something you were holding perfectly still start to move! I didn’t know then about the extremely subtle muscle movements that would set it in motion. I did try to test it by tying it to bits of furniture and seeing if it would move without a human touching the string (it would, but erratically, and probably had something to do with the air movements created as I shouted at it). Even back then, deep in the clutches of woo, there was apparently a scientific bit of my mind screaming to get out. It’s all a bunch of rubbish, of course – if it wasn’t, I would’ve died in July of 2008, according to it. So much for the stone’s power of prediction! But it’s gorgeous stuff, and its true nature is far more interesting than the woo we attached to it.

Thanks for the story, Dana!


“rutile, n.” The Oxford English Dictionary. 2nd ed. 1989. OED Online. Oxford University Press. 2 October 2011.


*That’s the consensus we’ve reached on Twitter and Facebook, anyway… please let me know if you have additional information on rutilated quartz formation.

***Thanks to Chuck Magee for suggesting this week’s word. Thanks to Tanya Ewing, Paul Glasser, and Dana Hunter for providing pictures. Thanks also to Dana for her wonderful woo-woo rutilated quartz story. Thanks to Erik Klemetti, Matthew Garcia, and Christie Rowe for an interesting Twitter and Facebook discussion about the origins of rutilated quartz.***