Rutilated quartz is transparent quartz that contains needles of rutile, a titanium dioxide mineral. The needles are usually golden, reddish or silver and can be fine as hair or thick as a pencil lead. The trade has called the finest material Venus hair stone for centuries. Most gem rutilated quartz comes from Brazil, and cutters shape it to show off the needles.
What it is
Quartz is silicon dioxide, the same mineral as amethyst and citrine. In rutilated quartz, the host is usually colorless rock crystal or light smoky quartz. Rutile, titanium dioxide, forms long, thin crystals that are typically golden yellow, red-brown or reddish copper, and sometimes silvery. Very thin rutile looks golden. Thicker needles look darker, nearly black.
The rutile was trapped inside the quartz as both minerals grew. Mineralogists call these protogenetic or syngenetic inclusions: the rutile either formed before the quartz and was engulfed, or grew at the same time.
How it forms
Rutilated quartz forms in hydrothermal veins and in alpine-type fissures, open cracks in metamorphic rock that fill with hot, mineral-rich water. Titanium in the fluid crystallizes as rutile needles. Quartz growing in the same space overgrows them and locks them in place.
Rutile needles in quartz often grow in a radiating star or spray. Some rutile also grows on a hematite base, producing golden needles that radiate from a flat, black hexagonal plate. These star patterns are especially popular with collectors and come mostly from Brazil.
Much finer rutile needles in quartz and corundum also create silk and asterism. In star rose quartz and star sapphire, microscopic rutile needles reflect light in a star pattern. The page on gemstone optics explains asterism.
Venus hair and other names
Venus hair stone (also called Veneris crinis or angel hair) refers to fine golden rutile in clear quartz. The name ties the needles to the golden hair of the goddess Venus in European tradition. Flèches d'amour, French for arrows of love, describes the same material.
Other inclusion types in quartz get their own trade names:
- Tourmalinated quartz contains black needles of schorl tourmaline.
- Actinolite quartz has green needles.
- Goethite and hematite quartz shows red to brown fans and tufts.
- Strawberry quartz has red specks of hematite or lepidocrocite.
Tourmalinated quartz
Tourmalinated quartz is the closest relative of rutilated quartz. Its black needles are schorl, the iron-rich black tourmaline. The needles are usually thicker and more brittle than rutile, often with a triangular cross-section and fine striations along their length. They look black and opaque, while rutile is shiny and metallic with a golden or red tone.
Tourmaline needles fracture more readily, so tourmalinated quartz often shows small breaks where needles reach the surface. Brazil is the main source. The material is popular for beads, cabochons and men's jewelry.
Sources
Brazil is the main source of fine rutilated quartz, especially Bahia and Minas Gerais. The gems of Minas Gerais page covers the Brazilian gem trade. Madagascar, Australia, Pakistan, Norway, Switzerland and the United States also produce it.
About rutile
Rutile is a titanium dioxide mineral that crystallizes in the tetragonal system. It has a very high refractive index, roughly 2.6 to 2.9, and an adamantine to metallic luster, which is why even thin needles catch the light inside quartz. Natural rutile crystals large and clear enough to facet are rare, and most are deep red to black.
Synthetic rutile was first grown around 1948 and sold as a diamond simulant under several trade names. Its dispersion of about 0.28 is far higher than diamond's, so it shows an obvious rainbow fire, and it is soft at about 6 to 6.5. Strontium titanate and later cubic zirconia replaced it. The page on cubic zirconia covers the simulants that followed.
How rutilated quartz is cut
Cutters choose the shape to display the needles. Thick, dense material becomes cabochons, beads, spheres and carvings. Clear material with fine needles is often faceted, which adds sparkle but can make the needles harder to see.
Many cutters use simple shapes with large, flat facets, such as checkerboard or step cuts, so the needles are visible through the table. They orient the stone so the densest, most attractive needles run across the face, and they avoid cutting through needles at the surface where they could leave pits. The gemstone cut shapes and styles page describes these cuts.
Judging quality
Value depends on clarity of the host, the color and density of the needles, and the pattern. Clear, colorless quartz with dense, evenly spread golden needles is the most sought after. Radiating stars on hematite plates and fine, even golden needles command higher prices than random dark needles in cloudy quartz.
Fractures, needles that break the surface and a hazy host lower value. Rutilated quartz is rarely treated, though some material is filled or coated. Glass imitations with embedded fibers exist but are easy to separate by hardness and bubbles.
Durability and care
Rutilated quartz has a hardness of 7 and no cleavage, so it suits most jewelry. Heavily included stones can be more fragile, especially where needles reach the surface. Clean with warm soapy water and a soft brush. Avoid ultrasonic cleaners for heavily included stones, since vibration can stress needles at the surface. The cleaning jewelry safely page has more detail. Avoid sudden temperature changes, which can crack quartz.
Frequently asked questions
Is rutilated quartz natural?
Yes. Rutilated quartz forms naturally when rutile needles are trapped inside growing quartz crystals.
What is the difference between rutilated and tourmalinated quartz?
Rutilated quartz has golden, reddish or silver rutile needles. Tourmalinated quartz has black tourmaline needles.
Can rutilated quartz be worn every day?
Yes. It is as hard as other quartz and holds up well in rings, pendants and earrings, though heavily included stones need gentler handling.
Why are the needles golden?
Thin rutile crystals look golden because of how they transmit and reflect light. Thicker crystals look red-brown or nearly black.