Short answer: rutilated quartz is clear quartz filled with fine, needle-like crystals of the mineral rutile. The needles usually look golden, but they can also be silver, copper red or black. Unlike most gems, where inclusions lower the value, rutilated quartz is prized for them. It is sometimes called Venus' hair stone. Quartz with black needles of tourmaline instead is called tourmalinated quartz.
What is rutilated quartz?
Rutilated quartz is a variety of quartz that contains acicular, or needle-like, inclusions of rutile. The host is usually transparent rock crystal, the colorless form of quartz, which lets the needles show clearly. The needles can be scattered at random or grouped in bundles, sometimes arranged like a star, and they can be sparse or so dense that the quartz looks nearly opaque.
What is rutile?
Rutile is a mineral made of titanium dioxide (TiO2), the most common natural form of that compound. Its name comes from the Latin rutilus, "red", for the deep red color some specimens show when light shines through them. Rutile is also an important ore of titanium, and powdered, it is the brilliant white pigment used in paints and plastics.
Rutile has one of the highest refractive indices of any known crystal, which is part of why the thin needles catch the light and glint inside the quartz.
Rutile was first described as a mineral in 1803 by the German geologist Abraham Gottlob Werner. On its own it forms brown, reddish brown, red and yellow crystals, rates 6 to 6.5 on the Mohs scale, and has an adamantine to metallic luster. Inside quartz, it is protected by a harder host.
Rutile in other gems
Rutilated quartz is the most visible place to see rutile, but the same mineral hides in more famous gems.
- Silk in sapphire and ruby: fine needle-like inclusions in sapphire, commonly rutile, are called silk. In ruby, heat treatment is often used to dissolve silk, and gemologists use natural rutile needles to help tell natural rubies from synthetic ones.
- Star sapphires and star rubies: when a stone with dense, oriented rutile needles is cut as a dome-shaped cabochon, the needles reflect light into a star. This effect is called asterism. The Star of India, a 563.35 carat star sapphire, is one of the best-known examples and is held by the American Museum of Natural History in New York.
In rutilated quartz the needles are large enough to see one by one, rather than as a silky glow or a star.
What colors are rutilated quartz?
- Golden rutilated quartz is the most common and best known. Brightly golden needles are generally the most valued.
- Silver and copper-red rutile also occur.
- Black rutilated quartz has dark rutile needles. It looks very similar to tourmalinated quartz.
Rutilated quartz vs tourmalinated quartz
Both are clear quartz with dark needle-like crystals inside, and they are easy to confuse.
- Rutilated quartz contains rutile, titanium dioxide. Its needles are usually fine, glinting golden to reddish or silver hairs.
- Tourmalinated quartz contains schorl, black tourmaline. Schorl can form tiny, dense needles inside quartz. Its strands are black, may be fine or thick, and may run parallel or crisscross.
When needles are black, telling the two apart for certain can need a gemologist. The tourmaline guide covers black tourmaline itself.
Rutile stars
In some rutilated quartz, the rutile grows outward from a flat crystal of hematite. The six-sided symmetry of the hematite controls the direction of the needles, forming a six-legged star. Complete six-ray stars are the hardest to find and the most valuable.
Where does rutilated quartz come from?
- Brazil is the leading producer, mainly from Minas Gerais, known for golden and coppery needles.
- Madagascar produces quartz with golden and red rutile.
- Pakistan: the Gilgit-Baltistan region yields smoky quartz with golden rutile.
- India, Namibia and the United States, including Arkansas and North Carolina, also produce it.
What makes rutilated quartz valuable?
Value depends on the host and the needles together:
- Clarity of the quartz: the clearer the rock crystal, the better.
- Color of the needles: brighter gold is generally valued more.
- Pattern: the more uniform the needles and their direction of growth, the higher the value. The rutile should form a noticeable, attractive design.
- Stars: complete six-ray stars are rare and especially prized.
What is rutilated quartz traditionally associated with?
In modern crystal traditions, golden rutilated quartz is associated with light, energy and clarity, echoing its glinting gold threads. Its old name, Venus' hair stone, ties it to the goddess of love and beauty.
These are traditions and beliefs. They are part of why people choose rutilated quartz, not properties you can measure in the stone.
Raw, tumbled and polished rutilated quartz
Rutilated quartz is used as a gemstone and is also sold as natural crystals and as polished points, spheres and tumbles. Polishing a clear face lets you look deep into the needles.
How do you care for rutilated quartz?
- Rinse off dust before you wipe it. Dust can be as hard as the stone itself, 7 on the Mohs scale, and wiping it across the surface leaves fine scratches that dull the polish over time.
- Wash it with warm water and mild soap, then dry it.
- Store it apart from harder gems such as sapphire and diamond, which can scratch it.
How can you tell real rutilated quartz?
- Look closely at the needles. Natural rutile needles are crystals inside the quartz, straight and sharp, often in bundles or sprays.
- Check the host. Quartz is 7 on the Mohs scale, harder than glass and steel, so a steel blade will not scratch it.
- Buy from sellers who name the inclusion, rutile or tourmaline, since the two are easily confused.
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Rutilated and tourmalinated quartz in stock
Frequently asked questions
What are the needles in rutilated quartz?
They are crystals of rutile, a titanium dioxide mineral, trapped inside the quartz. They are usually golden but can be silver, copper red or black.
What is the difference between rutilated and tourmalinated quartz?
Rutilated quartz contains rutile needles, usually golden. Tourmalinated quartz contains black tourmaline (schorl) needles. Black rutile can look very similar.
Is rutilated quartz valuable?
Values vary widely. Clear quartz with bright, golden, evenly arranged needles is valued most, and complete six-ray rutile stars are rare and especially prized.
What is rutilated quartz traditionally associated with?
In crystal traditions it is associated with light, energy and clarity. These are traditional meanings rather than measurable properties.
Where is rutilated quartz found?
Brazil is the leading producer, mainly from Minas Gerais. It also comes from Madagascar, Pakistan, India, Namibia and the United States.
Sources
- Wikipedia, Rutilated quartz: https://en.wikipedia.org/wiki/Rutilated_quartz
- Wikipedia, Rutile: https://en.wikipedia.org/wiki/Rutile
- JCK, Rutilated Quartz: https://www.jckonline.com/magazine-article/rutilated-quartz/
- Wikipedia, Asterism (gemology): https://en.wikipedia.org/wiki/Asterism_(gemology)
- Minerals.net, Schorl: https://www.minerals.net/mineral/schorl.aspx
- Natural Gemstones, Major rutilated quartz mining areas: https://naturalgemstones.com/education/major-rutilated-quartz-mining-areas/