Myth of the Month: Oil Spills - the Truth About Cedarwood Oil
whether an emerald enhancement substance is natural or synthetic is beside the point. What matters is the impact and durability of the substance.
Nevertheless, many dealers cling to the misguided notion that natural oils or resins are the only legitimate enhancement agents for emeralds. Using this rationale, they defend a preference for cedarwood oil.
It's a bad idea. Here's why:
What is Cedarwood Oil?
Walk into a store that specializes in toiletries. You'll find hundreds of products like cosmetics, perfumes, and soaps which contain aromatic oils. These substances can be extracted from flowers, plants, roots and woods and are called "essential oils." The word essential as used in this context refers to "essence" because these botanical oils gave preparations to which they were added a characteristic odor or taste that was thought to be unique and defining - hence essential.
One of the most popular essential oils is that taken from cedar trees, a name given to several species of evergreen, and known as cedarwood oil. Many botanists believe that most varieties of cedar are variants of one species, the cedar of Lebanon. Cedar forests were often in the mountainous areas of the Mediterranean, which explains why cedarwood extracts were commonly used by the Egyptians, Greeks and Romans for odiferous oils and ointments - both for local consumption and trade.
Cedarwood as an Emerald Enhancer
One incidental use of this resinous oil may have been as a gemstone enhancement to hide complexion problems. We say "may" because this is still mostly a matter of conjecture. In a Middle Ages chemistry text written by the Arab scholar Schehab ed-din Abul Abbas Achmed, we find the following brief, rather cryptic reference to oiling: "When an emerald is found it is thrown into hot oil, then into wood shavings and wrapped in linen or some other material."
This solitary note suggests that emerald - then a catchall term for green gems - was commonly enhanced. But we are not told the exact reasons. Was it to hide emerald's numerous surface-breaking fissures? We can only presume, but not prove, this.
The only two gem treatises from antiquity which refer specifically to emerald enhancement - an Egyptian papyrus and a work by Pliny the Elder from the first century AD - are not explicit about the reasons for and results of this process. Strangely, Pliny only mentions one purpose for treating emeralds: "quench crackling," a heating process which induces - not hides - surface cracks.
Did the ancients have vastly different tastes from our own? Or was ancient emerald, found mostly in Egypt, so included and opaque to begin with that the ancients decided to make a virtue of necessity and create a spider web effect on the surface of stones? No one knows for sure.
The only thing we know is that cedarwood oil could have lent itself to camouflaging gem complexion problems just as it lent itself to camouflaging human complexion problems.
Chemical Dependence
Some time around 1962 emerald dealers in Colombia began immersing stones in cedarwood oil to perform the task for which it is best known in the jewelry industry: improving appearance by hiding surface-breaking fissures. By then, commercial cedarwood was available in synthetic form, which made it less expensive and, it is said, more stable. Although all-natural versions of this oil were still available, most of the chemical companies which supplied the cedarwood oil used by gem dealers were adding synthetics to their formulations. In short, it could no longer be assumed that cedarwood oil was natural. GIA has even said this in a lengthy article, "Emerald Filling Substances," published in the Summer 1999 issue of Gems & Gemology. To date, we know of no independent chemical analysis of the cedarwood oil compounds most commonly used for emerald enhancement. What we do know is that most of them contain synthetic additives.
Cedarwood oil was originally adopted for use because it was an improvement over previous fillers. Unfortunately, like other oils, it too dehydrates over time. Hence stones need periodic re-enhancement. Besides being impractical, re-enhancement with cedarwood oil is tricky and time-consuming. Stones must be thoroughly cleaned before a filler can be reintroduced. Most dealers do not have the expertise or equipment to do this. We often receive emeralds in our lab that have been enhanced repeatedly. You can imagine the cumulative effect on a stone's beauty and durability of injecting resinous oils at high pressure.
That's why Colombia's emerald dealers began to experiment with polymers like Palma and Opticon. Cedarwood oil was good only for short-term cosmetic improvement. A more permanent solution was needed. The bottom line: Cedarwood oil is ill-advised for three reasons:
- It cannot be claimed to be a natural substance since it usually contains synthetic ingredients.
- It has failed to prove itself as a permanent enhancement agent.
- Repeated use threatens the beauty and durability of stones.
