Rutile Identification Guide

What Rutile Looks Like

Rutile is titanium dioxide (TiO2) and is one of the most common natural titanium minerals. In hand specimen it ranges from reddish-brown and blood-red to nearly black, with rarer golden and yellow tones. Its standout feature is a brilliant adamantine to submetallic luster that almost looks wet or oily. Crystals are typically slender prisms or needles with strong vertical striations along their length, often terminated by pyramid faces. Rutile frequently forms knee-shaped (geniculated) twins and rosette-like clusters, and as gold-colored needles it famously occurs as inclusions inside quartz ("rutilated quartz").

Step-by-Step Field Checklist

1. Look at luster first. A glassy stone is not rutile; rutile glitters with a near-diamond or metallic-adamantine shine.
2. Check color and transparency. Most field rutile is opaque to translucent reddish-brown to black; thin needles transmit deep red light at the edges.
3. Inspect crystal form. Look for long, square-cross-section prisms with deep lengthwise striations, elbow twins, or radiating sprays.
4. Streak it. Rub on unglazed porcelain — rutile gives a pale brown to yellowish streak, never black like magnetite or hematite.
5. Test hardness. Rutile is Mohs 6–6.5; it scratches glass and a steel knife will not scratch it easily.
6. Feel the weight. With a specific gravity of about 4.2–4.3, it feels noticeably heavy for its size.

Key Diagnostic Tests

• Hardness: 6–6.5 — scratches glass, resists a knife.
• Streak: light brown, yellowish, or pale gray — diagnostic against black-streaking iron minerals.
• Luster: adamantine to submetallic — brighter than almost any look-alike.
• Cleavage: distinct prismatic {110} cleavage; fracture is uneven to conchoidal.
• Specific gravity: ~4.2, distinctly dense.
• Magnetism/acid: not magnetic and does not react to acid (helps rule out magnetite and carbonates).

Common Look-Alikes and How to Tell Them Apart

• Cassiterite (SnO2): very similar adamantine luster and habit, but cassiterite is harder (6.5–7) and much denser (SG ~7), with a pale streak; heft is the giveaway.
• Hematite/magnetite: these give a red-brown or black streak and magnetite is strongly magnetic; rutile is non-magnetic with a pale streak.
• Brookite and anatase: both are TiO2 polymorphs; brookite forms tabular blades and anatase forms steep bipyramids, while rutile is prismatic and striated.
• Goethite/limonite: softer, earthier luster, brown streak that is darker and more ochreous.
• Tourmaline (schorl): also striated prisms, but schorl is matte to vitreous (not adamantine) and gives no metallic sheen.

Where Rutile Is Found

Rutile is widespread as an accessory mineral in granites, gneisses, schists, and high-grade metamorphic rocks. It concentrates in heavy-mineral placer sands along beaches and rivers because of its density and durability. Notable specimen localities include Graves Mountain (Georgia, USA), Magnet Cove (Arkansas), the Alps, and Brazil, where golden needles are mined inside quartz.