How to identify Cat's Eye Chrysoberyl

To correctly identify Cat's Eye Chrysoberyl (Chrysoberyl (variety Cymophane)), 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 honey-yellow, yellowish-green, green, or brownish-yellow. Can also be gray or brown.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous to greasy.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Smooth when polished; rough on fracture surfaces.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Orthorhombic system, often forming tabular or short prismatic crystals, frequently twinned, especially in pseudohexagonal forms. When cut en cabochon, the chatoyant effect is visible.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Distinct on {110}, indistinct on {010} and {001}.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Found in granitic pegmatites, mica schists, and sometimes in contact metamorphic deposits. Due to its high specific gravity and hardness, it is also concentrated in alluvial and eluvial placer deposits.

Key Facts

Hardness

8.5 (Mohs scale)

Specific Gravity

3.71 - 3.75

Crystal System

Orthorhombic

Color

Yellow, yellowish-green, green, brownish-yellow, gray, brown

Luster

Vitreous to greasy

Transparency

Transparent to translucent

Fracture

Conchoidal to uneven

Cleavage

Distinct on {110}, indistinct on {010} and {001}

Composition

Beryllium Aluminum Oxide (BeAl2O4)

Physical characteristics

• Crystal Habit: Tabular, short prismatic, often twinned (pseudohexagonal), massive, granular. Chatoyancy is best observed in cabochon cuts.
• Cleavage Type: Distinct in one direction ({110}), indistinct in two others ({010}, {001}).
• Fracture Type: Conchoidal to uneven, brittle.
• Tenacity: Brittle
• Luster Type: Vitreous to greasy

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