Moh’s Hardness: 7.5-8
Refractive Index: 1.57-1.60
Critical Angle: 39.87°
Specific Gravity: 2.65-2.75
Fracture: Conchoidal, tough
Heat Sensitivity: Yes, especially depending on treatments
Birefringence (double refraction): Weak (.006-.009)
Crystal Structure: Hexagonal
Treatments: Almost all Emeralds are treated to improve color and durability. Assume that any Emerald you see is treated. I personally do not agree with a lot of the Treatments used on Emeralds… Here is an article on Emerald treatments and my opinion on them…
What I prefer to polishing with: Cerium oxide with a Spectra Ultralap.
Jeff’s Comments: I seldom cut Emeralds, most of the rough is low quality in my opinion and I do not like to cut oiled, or opticoned rough. If you want to cut some for the color, I suggest cutting man-made Emerald…
Design Notes: Mostly Emerald cuts and step cuts because the crystals are usually small long and narrow.