Emerald
from the Antique Jewelry University
The color of emerald, the birthstone of the month May, has once been described as "warm green of a meadow in spring"[1]. It's grass green primary hue is usually modified by slight bluish or yellowish undertones. The greener the color, the more desirable the stone becomes and top quality stones from Colombia are unrivaled in their - chromium induced - silky hue.
This high-end variety of the beryl family has long been regarded as one of the most precious of all gemstones, surpassed only by ruby. Cellini in the 16th century narrated that the value of a fine emerald would be half the price of a like ruby, but was four times more valuable than diamond[2].
Emerald is a type III gemstone on the GIA clarity scale, meaning they are usually included with imperfections which may detract from their beauty. It is a longtime practice that these stones are impregnated with oils to mask these internal features. Polymer and resin type fillers are also used to reduce the visibility of the fine fissures that reach the surface and therefor improve clarity. This is a common practice that has been widely accepted for centuries and as always; beauty is forgiven many flaws. Only few emeralds have undergone no treatment and those command extremely high prices.
| Gemological information for emerald | |
|---|---|
| Color | Green with blue or yellow tones |
| Crystal structure | Hexagonal |
| Family | Beryl |
| Refractive index | 1.566-1.600 |
| Durability | May be fragile/brittle |
| Hardness | 7.5-8 |
| Similar stones | Confusion is possible with tourmaline, diopside, fluorite and green glass |
| Treatments | Emerald is routinely fracture filled and/or oiled |
| Country of origin | Brazil, Colombia, Africa |
| Emerald care | |
| Ultrasonic cleaning | Not safe |
| Steam cleaning | Not safe |
| Warm soapy water | Safe |
| Chemical attact | Usually resistant |
| Light sensitivity | Stable |
| Heat sensitivity | Very sensitive, unstable |
Notes
Sources consulted
- The Treatises of Benvenuto Cellini on Goldsmithing and Sculpture, Ashbee, C.R.. ISBN 0486215686