How to identify Rutile

To correctly identify Rutile (TiO2), check each of these features in order. Many rocks and minerals look alike, so cross-reference multiple properties before deciding.

Step-by-step identification

1. 1

   Color

   Overall color and any zoning or banding

   Typically reddish-brown, dark red, yellowish-brown, black; rarely golden-yellow or violet. Transparent varieties can be golden-yellow.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Adamantine to submetallic, sometimes metallic on fracture surfaces.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Often occurs as prismatic crystals, sometimes acicular (needle-like) or massive. Can be granular.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Tetragonal system, typically forming prismatic crystals with square cross-sections, often striated parallel to the c-axis. Characteristic twinning, especially geniculate (knee-shaped) twins, is common. Also found as acicular inclusions.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Distinct to good on {110} and {100}, but often imperfect or difficult to observe due to fracture.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in igneous rocks (e.g., granites, syenites, kimberlites), metamorphic rocks (e.g., gneisses, schists, eclogites, granulites), hydrothermal veins, and as a heavy mineral in placer deposits and sedimentary rocks.

Key Facts

Hardness

6 - 6.5 on Mohs scale

Specific Gravity

4.23 - 4.30 g/cm3 (can vary slightly with impurities)

Crystal System

Tetragonal

Color

Reddish-brown, dark red, yellowish-brown, black; rarely golden-yellow or violet

Luster

Adamantine to submetallic

Transparency

Transparent to opaque

Fracture

Subconchoidal to uneven

Cleavage

Distinct to good on {110} and {100}, but often imperfect

Composition

Titanium dioxide (TiO2)

Physical characteristics

• Crystal Habit: Prismatic, acicular, massive, granular; often twinned (geniculate twins common)
• Cleavage Type: Prismatic (distinct to good on {110} and {100})
• Fracture Type: Subconchoidal to uneven
• Tenacity: Brittle
• Luster Type: Adamantine to submetallic

Explore Rutile