How to identify Zircon

To correctly identify Zircon (ZrSiO4), 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 brown, reddish-brown, yellow, green, blue, or colorless. Color can be highly variable even within a single crystal or locality.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Adamantine to vitreous, often appearing brilliant.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Usually occurs as small, well-formed prismatic crystals, often with pyramidal terminations. Can also be found as rounded grains in sedimentary rocks.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Tetragonal system, typically forming square prisms terminated by pyramids. Crystals are often small, ranging from microscopic to several millimeters, though larger crystals are known.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Poor to indistinct on {110} and {111}. Fracture is more common than cleavage.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Common accessory mineral in igneous rocks (especially granites, syenites, and their volcanic equivalents), metamorphic rocks (gneisses, schists), and as detrital grains in sedimentary rocks (placers, sandstones). It is particularly resistant to weathering and alteration.

Key Facts

Hardness

6.5-7.5 on the Mohs scale

Specific Gravity

4.6-4.7 (can vary slightly with metamictization and trace element content)

Crystal System

Tetragonal

Color

Highly variable: colorless, yellow, golden-yellow, orange, red, brown, green, blue. Often zoned.

Luster

Adamantine to vitreous, sometimes greasy in metamict varieties.

Transparency

Transparent to opaque

Fracture

Conchoidal to uneven

Cleavage

Poor to indistinct on {110} and {111}

Composition

Zirconium silicate (ZrSiO4), with common substitutions of Hf, U, Th, REEs.

Physical characteristics

• Crystal Habit: Prismatic crystals with pyramidal terminations, often small and euhedral. Can also be anhedral or rounded detrital grains.
• Cleavage Type: Poor to indistinct, typically not observed in hand specimens.
• Fracture Type: Conchoidal to uneven, brittle.
• Tenacity: Brittle
• Luster Type: Adamantine to vitreous

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