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Sunday, November 11, 2007

The Emerald Story

Emerald Simulants (synthetics and imitations)

Synthetic emeralds: Synthetic emeralds are man-made emeralds which have the same physical, chemical and optical properties of a natural emerald. Man has very skillfully duplicated this natural green stone so that it is sometimes extremely difficult to tell the difference. However, with the aid of magnification and other tests, a synthetic readily reveals its true identity. Synthetic emeralds have been in the market for several decades, but it’s only now, due to sophisticated mass production techniques that they have become more prevalent and a cause for concern. In the past synthetics were deceptively passed off as natural emeralds by dealers, but today they are now being successfully marketed as synthetics or lab-created by such companies as the San Francisco-based Chatham Inc, Russian-based Tairus, and others.

The techniques employed for the production of synthetic emeralds are:
- Flux growth
- Hydrothermal growth

Flux method: A flux is a chemical compound which when melted has the ability to assist another substance to melt at a temperature lower than would be normal for that material. The chemical components of emerald may be dissolved with an appropriate flux while being held within a platinum-lined crucible. Upon cooling, crystals of synthetic emerald are formed. Chatham employs the flux method for the production of his synthetic emeralds.

Typical inclusions:
- Solid masses of residual flux which appear cloudy.
- Wispy veils—look like thin veils blowing in breeze. Resemble natural liquid fingerprints, but may be more dense.
- Venetian-blind—refers to the appearance of very fine straight line growth zoning which takes on the appearance of venetian blinds.

Hydrothermal process: Of all the synthetic gem growth techniques, this process mimics most closely the process of nature for the creation of emeralds. As the name indicates, it involves water, heat and pressure. Nutrient material (chemical compound for emerald) is placed in an autoclave or ‘bomb’ along with a number of seed crystals located towards to upper (eventually cooler) part of the vessel. Heated water under high pressure dissolves the nutrient and through convection, the chemical needed to grow emerald are deposited on the seed crystal. These crystals now continue to grow so long as the conditions for growth remain and there is a supply of the nutrient.

Typical inclusions:
- Liquid feather with the appearance of fingerprints.
- Distinct fine line zoning.
- Arrow head zoning.
- Nail-head-like phenakite inclusions.

Emerald Story (continued)

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