Cat's Eye Green Tourmaline Identification Guide
Identify cat's eye green tourmaline by its green body, chatoyant band, and strong pleochroism, and tell it from cat's eye chrysoberyl and quartz.
Read the full Cat's Eye Green Tourmaline encyclopedia entry →
What Cat's Eye Green Tourmaline Looks Like
This is green tourmaline (elbaite) that shows chatoyancy from dense parallel needle or tube inclusions, producing a soft cat's eye band on a cabochon. Tourmaline cat's eyes tend to have a slightly broader, softer eye than chrysoberyl.
- Color: green — from grassy to bluish- or yellowish-green.
- Luster: vitreous.
- Transparency: translucent (slightly silky from inclusions).
- Effect: a single light band across the dome.
Step-by-Step Field-ID Checklist
- Confirm the eye: under one light, a band glides across the cabochon.
- Check pleochroism: tourmaline shows strong color change when viewed from different directions — rotate and watch the green darken/lighten.
- Hardness test: ~7–7.5; scratches glass.
- Look at the inclusions: numerous parallel hollow tubes (a tourmaline hallmark) cause the eye.
- Note the elongated origin: tourmaline grows as long striated prisms, so rough often shows lengthwise tube structure.
Key Diagnostic Tests
- Mohs hardness: 7–7.5.
- Streak: white.
- Cleavage: poor/indistinct; uneven to conchoidal fracture.
- Density: ~3.0–3.1 g/cm³.
- Refractive index: ~1.62–1.64, with strong birefringence.
- Pleochroism: strong — diagnostic for tourmaline.
Common Look-Alikes
- Chrysoberyl cat's eye: harder (8.5), denser (~3.7), sharper eye, and weak pleochroism; density and RI separate it.
- Cat's eye quartz (greenish): softer (7), lower RI (~1.55), lower density (~2.65), weak pleochroism.
- Cat's eye green beryl: lower RI (~1.57) and weaker pleochroism than tourmaline.
- Green glass cabochon: bubbles, no pleochroism, and a flat mechanical eye if fiber-optic.
Where Cat's Eye Green Tourmaline Is Found
It comes from granitic pegmatites, especially in Brazil (Minas Gerais), Madagascar, Mozambique, and Sri Lanka. Chatoyant material requires abundant parallel growth tubes, so it is a select portion of pegmatite tourmaline, cut as cabochons.
Frequently asked questions
What causes the cat's eye in green tourmaline?
Dense, parallel hollow tubes or needle inclusions within the tourmaline reflect light into a single band when the stone is cut as a cabochon across them.
How do you tell cat's eye green tourmaline from chrysoberyl cat's eye?
Tourmaline shows strong pleochroism, is softer (7–7.5 vs 8.5), and less dense (~3.05 vs ~3.7). Chrysoberyl has a sharper eye and minimal pleochroism.
Is cat's eye tourmaline pleochroic?
Yes, strongly. Rotating the stone changes how light and dark the green appears, which is a reliable clue that you are looking at tourmaline rather than quartz or beryl.
What hardness is cat's eye green tourmaline?
About 7–7.5 on the Mohs scale, hard enough to scratch glass and suitable for jewelry, though softer than chrysoberyl.