THE VALUE OF CEDARWOOD OIL - written in 1998
Amidst the touting of new, high-tech fracture-fillers for emeralds and the decrying of Opticon and palm oil, cedarwood oil has been overlooked. Let's look into the benefits of the venerable cedarwood oil and see why it remained the standard of the Colombian emerald industry for over 20 years.
THE PERFECT R.I.
1. The most beautiful of all the properties of cedarwood oil is it's refractive index of 1.515. You would think that that R.I. was designed by a team of research scientists although it probably just happened that way. 1.515 is just close enough to the 1.576 1.583 of emerald to neatly diminish the visibility of fractures without making them totally invisible; the face-up view of the stone is clean but under a loupe the faint outline of the fracture is apparent (See Fig. 1 & 2). This gives assurance and confidence to the buyer that he knows what he is getting.
Opticon on the other hand, in spite of good transparency and durability, was rejected by the industry as a fracture-filler for emeralds because it has a refractive index (1.570) that was too close to emerald. That high R.I. made Opticon almost invisible in the fractures, thereby confusing buyers because they could not always tell what they were looking at. Palm oil (R.I. - 1.570) was rejected for the same reason as well as having severe stability problems.
FIG. 1 - [Left] (Before) This 1.05 carat emerald has two small fissures coming to the surface that will accept fissure-filling.
FIG. 2 -[Right] After fissure-filling with cedarwood oil, the face-up appearance of this emerald is greatly improved. Note that the outline of the fissures are still visible, permitting the buyer to know about the small fissures even if it was not disclosed by the seller.
NO FLASH EFFECTS
2. Another benefit of cedarwood oil's beautiful R.I. is that it is not so close to that of emerald that it creates blue or orange flash effects. Resins with slightly higher R.I.'s like Opticon and palm oil create flash effects.
TRACK RECORD
3. For over 20 years, Colombia has been providing the world with emeralds that are clarity enhanced with cedarwood oil. This amounts to over 5 million individual stones! Complaints about temporary or deceptive enhancements never arose until palm oil (which discolors badly over time) began to be used in large amounts in the early 1990's. The stability and familiarity of cedarwood oil has been known and accepted as standard in the industry for over 20 years.
Critics say that cedarwood oil discolors to a brownish orange over time but in the thin films encountered within fractures it is still colorless. Regardless, slight coloration is not a detriment; fracture-filling experts in the glass industry regularly tint their fracture-fillers to an amber color to reduce unwanted reflectivity.
PREDICTABLE BEHAVIOR
4. Experienced emerald traders are accustomed to the behavior of cedarwood oil; during the first few weeks after oil treatment, a tiny amount of oil seeps out of the fractures (this usually happens due to changes in temperature and pressure due to handling and traveling). This seepage causes an insignificant to slight alteration of the visible appearance of the stones (hardly noticeable except to the owner of the goods). After this period of setting in, the treatment is highly stable. Reputable dealers do not re-treat or 'refresh' their stones after that, choosing to serve their customers with a product that will not change on them and cause disfavor. This is how billions of dollars worth of emeralds treated with cedarwood oil have been sold over the years.
CEDARWOOD: THE HONEST OIL
5. This unique porperty of stably filling the small and medium fractures while seeping out of the large fractures gives cedarwood oil the property of "automatic disclosure"; if the seller does not disclose the significant or large fractures, then the oil will disclose by leaking out; a very 'honest' oil!
ENDORSEMENT FROM TRADE ASSOCIATIONS IN BOGOTÁ
6. After considering new experimental treatments like Groom/Gematrat and others, the Colombian Association of Cutters, the Colombian Association of Exporters (ACODES), and the Brokers Association in Bogotá have stayed with Cedarwood oil. They may in the future endorse a high-tech filler but only after thorough testing.
PHOTO CAPTIONS
FIG. 1 - This 1.05 carat emerald has one small fracture coming to the surface that will accept fracture-filling.
FIG. 2 - After fracture-filling with cedarwood oil, the face-up appearance of this emerald is greatly improved. Note that the outline of the fracture is still visible, permitting the buyer to know about the small fracture even if it was not disclosed by the seller.