Unheated Concave-Cut Tourmaline 1.87 (COT187)

1.87 Carat
Dark Blue-Green
Medium Dark 70-90
Free of Inclusions

GRADING REPORT COT187

• Identification: Natural Unheated & Untreated Tourmaline
• Carat: 1.87
• Shape: Oval Concave
• Measures: 9.92x6.84x4.61 (millimeter)
• Color Grade: Very Good
• Tone: MD70 to MD90
• Color Zoning: None
• Clarity: Free of Inclusions
• Cutting Grade: Excellent (precision concave cut)
  • Brilliancy: 50%
  • Depth: 67%
• Origin: Mozambique
• Treatment: None

Certificate No: IGI 208615067

Overall Grade: Excellent

Comment: Concave-cut dark blue-green tourmaline with opposing optical features: The gem is brightest in the center, where it is thickest and normally should be darkest, but here it results in an outward sparkling center, getting darker towards the thinner tips. The reason for this ususual sight can be found in the rough crystal shade but also in the concave facets, which are not flat but curved inwards. In this gem the cutter used concaves not only on the backside but also on the front (a first time to me). As clearly visible in the images this has all kinds of unusual effects from various angles an in changing light. The overall impression of the gem is dark blue-green, from MD70 in the center to MD90 in the outer rims. No inclusions are found even under the lens. Full IGI report, unheated and defined as verdelite but clearly bordering to indicolite. So far off the beaten track it deserves a medal for uniqueness. See side images! From the same cutter and origin as CTO129 but in many ways exactly the opposite. If you are looking for a special green gem in a gent's ring, look no further.