Source: Afghanistan, Brazil, Canada (Regal Ridge), Columbia, Madagascar, Pakistan, Zambia

Birthstone: May

The name “Emerald” (French: Émeraude, German: Smaragd, Spanish: Esmeralda) comes from the Greek word smaragdos; a name that was given to several gemstone minerals having little in common chemically, but sharing a similar bluish-green colour. An emerald is a form of Beryl, a mineral group that includes Aquamarine and Morganite. Emerald’s leaf-green colour is partially due to Allochromatic colouration from trace amounts of Chromium (Cr) and Vanadium (V) Impurities.

Emeralds, like all Coloured Gemstones, are graded using four basic parameters–the four C’s of connoisseurship: Colour, Clarity, Cut and Carat weight. Normally, in the Grading of coloured Gemstones, Colour is by far the most important criterion. However, in the grading of Emeralds, Clarity is considered a close second. A fine Emerald must possess not only a Pure Verdant Green hue as described below, but also a high degree of transparency to be considered a top gemstone.

In the 1960s, the jewellery industry changed the definition of Emerald to include the Green Vanadium-bearing Beryl. As a result, Vanadium Emeralds purchased as Emeralds in the United States are not recognized as such in the UK and Europe. In America, the distinction between traditional Emeralds and the new Vanadium kind is often reflected in the use of terms such as “Colombian emerald”.

Emerald is transparent to translucent member of the Beryl family of Minerals (Aquamarine, Morganite, Goshenite, Red Beryl) and is typically associated with Igneous rock. Emerald is Acyclosilicate of Beryllium and Aluminium, and owes its Green colour to Chromium and Vanadium, along with other trace coloring agents which include Beryllium (Berillium) (Be) Aluminum Silicate and Iron (Fe).

Identification

Formula mass:                         537.50

Color:                                      Green shades to colorless

Crystal habit:                           Massive to well Crystalline

Cleavage:                                Imperfect

Fracture:                                 Conchoidal

Mohs scale hardness:             7.5–8

Luster:                                     Vitreous

Streak:                                     White

Diaphaneity:                           Transparent to opaque

Specific gravity:                       Average 2.76

Optical properties:                  Uniaxial (−)

Refractive index:                     nω = 1.564–1.595,nε = 1.568–1.602

Birefringence:             δ = 0.0040–0.0070

Ultraviolet fluorescence:        None (some fracture-filling materials used to improve emerald’s clarity do fluoresce, but the stone itself does not)