Beryl

Emerald

Emerald is green beryl. Most natural emeralds carry visible inclusions, which the trade calls the jardin (garden), and most are oiled to make small fissures less visible.

Emerald
Natural emerald

At a glance

Mineral: Beryl, green from chromium and vanadium
Refractive index: 1.58
Dispersion (C–F): 0.009
Specific gravity: 2.72
Mohs hardness: 7.5–8
Wear: Hard but brittle because of its inclusions: protective settings, and no ultrasonic cleaning.

Emerald in Jart

The 2 looks in the studio's material library, with the values the renderer uses.

Optics of Emerald in Jart
Stone	Colour	RI	Dispersion C–F	Abbe	SG	Colour depth
Emerald	#16a76d	1.58	0.009	65	2.72	4.3 mm
Natural emerald	#16a76d	1.58	0.009	65	2.72	5 mm

RI refractive index (n_d). Dispersion C–F n_F − n_C, the spread between blue and red light; many gem tables quote the B–G figure instead (diamond 0.044, here 0.025). Abbe number: lower means more fire. SG specific gravity, used for carat estimates in Design Facts. Colour depth the path through the stone after which white light takes the stone's full colour; shorter paths look paler.

How it renders

With a refractive index of 1.58, a polished emerald facet reflects 5.1% of light that meets it face-on (diamond: 17.2%). Light inside the stone that meets a facet more than 39.3° from straight on cannot leave and is reflected back in; the smaller that angle, the more light a good cut returns to the eye (diamond 24.4°, quartz 40.4°).

Its dispersion (C–F) is 0.009, 36% of diamond's, which sets how much fire, the flashes of colour, a render shows under small, bright lights.

The natural emerald preset fills the stone with clouds and specks, the most of any precious stone preset, because a perfectly clean emerald looks synthetic to a jeweller's eye.