27.20ct Green Tourmaline rough, table view
27.20ct Green Tourmaline rough, front right view
27.20ct Green Tourmaline rough, back left view
27.20ct Green Tourmaline rough, pavilion view
27.20ct Green Tourmaline rough, back right view
27.20ct Green Tourmaline rough, front left view

27.20CT Green Tourmaline Faceting Rough | Uncut Gemstone

$217.60

Nigeria 27.20ct green tourmaline rough, medium green and peach tones, eye clean clarity, 27.56×9.9×9.9mm. Recommended shapes include round or emerald.

1 in stock

SKU: zHD8ZP-RFI0 Categories: ,

Technical Specifications & Gemological Properties

Specifications for 27.20CT Green Tourmaline Faceting Rough
Carat Weight 27.20CT
Dimensions 27.56 × 9.9 × 9.9mm
Origin Nigeria
Treatment None known
Color Medium Green (AB axis)
Clarity Grade Eye Clean
Gem family Tourmaline
Variety Green Tourmaline
Secondary color Peach (C axis)
Recommended shapes Round, Trillion, Emerald
Refractive Index 1.62–1.64 †
Hardness (Mohs) 7–7.5 †
Optic Character Doubly refractive, uniaxial (−), birefringence 0.018–0.020 †
Pleochroism Moderate to strong (dichroic) †
Specific Gravity 3.02–3.26 †

† Typical reference value for tourmaline; individual stones vary.

How to orient and cut this rough — Lapidary Guide

Description

This 27.20ct green tourmaline rough from Nigeria has a medium green tones on the ab axis and a peach c axis. This stone is eye clean. Trim to capture multiple beautiful peach colored round or trillion stones cut with the c axis, or trim for a pair of emerald shaped stones displaying the green color.

27.20CT Green Tourmaline Rough Specifications

  • Lapidary notes: Blocky shape for high yield; Clean rough; Open C-axis

Cutting Notes

Place the table parallel to the c-axis to showcase the medium green color. The rough has a blocky shape and an open c-axis, which supports a high yield for round or emerald cuts. Since the stone is eye clean, you can focus on maximizing the weight without navigating internal inclusions.

Tourmaline is brittle and sensitive to heat, so keep the stone cool and avoid heavy pressure during grinding. Be mindful of the critical angle around 38 degrees to prevent windowing in the pavilion. Because this variety is doubly refractive, you may see doubled facet edges during the polishing process.

Cutter’s tip: The blocky dimensions and open c-axis make this an excellent choice for a high-yield emerald cut.

Every stone is filmed on video before it is listed, so what you see is the stone you get. For background on Green Tourmaline, see the GIA Tourmaline guide. Browse more Green Tourmaline faceting rough from Jackson’s Gems.

Related Guides

New to cutting Tourmaline? See the Lapidary Guide.

Questions About This Green Tourmaline Rough

How does the color of this green tourmaline vary with orientation?

This stone shows medium green when looking across the c-axis and peach along the c-axis. To keep the green hue face-up, the table must be parallel to the c-axis.

What should I watch for when grinding the pavilion?

Pavilion angles near or below 38 degrees can cause light to leak out. Keeping angles above this critical angle prevents windowing.

Is this green tourmaline heat treated?

There is no known treatment for this specific stone. While some green tourmalines on the market are heated, most remain untreated.

Why do facet edges sometimes look doubled in tourmaline?

This is caused by birefringence, which is the difference between the two refractive indices. In tourmaline, this effect is high enough to be visible at the edges.

What are the risks when polishing tourmaline rough?

Tourmaline is brittle and can chip or crack if subjected to excessive pressure or heat. Using a cool lubricant and light pressure is recommended.

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