by Marc Gering
What is a Trapiche Emerald?
There are plenty of books and articles describing the beauty of the emerald, from its rich green tones to the jardin, (garden) inclusions that often occupy an emerald (and help to identify its origin) to its unique cutting properties. But there is very little information about this rarest form of emerald: the Trapiche Emerald.
The name trapiche comes from tra·pi·che (de azúcar), meaning “of sugar.” More specifically, trapiche emeralds are named for the grinding wheel used to process sugarcane in the region of Colombia, South America where they are most often found. In the figures below you can see the spoked structure in these gemstones that approximates the look of the grinding wheel.
How is a Trapiche Emerald Formed?
The unique design present in trapiche emeralds is not a case of asterism, as many have suggested. Trapiche emeralds are formed during a beryl crystal’s growth. Black carbon impurities fill in at the emerald crystal junction which forms a radial pattern with a six-pointed star effect. In some trapiche emeralds, inclusions consisting of albite, quartz, and a carbonaceous material (what some have referred to as lutite) outline a hexagonal beryl core, and they extend from it in spokes that divide the surrounding emerald material into six trapezoidal sectors.
First, the central, tapered core grows under hydrothermal conditions. Second, growth may slow or even stop for some time. Next, growth conditions change again, and both emerald and albite are formed. However, the hexagonal prism faces of the core crystal are able to maintain their uniform growth, producing pure emerald, while areas growing from the edges between prism faces are not and are filled by albite. This results in six sectors of clear emerald and six of predominantly albite and minor emerald. Thus, the central core and the six surrounding sectors of a trapiche emerald comprise a single, untwinned crystal.
Often, the hexagonal beryl center is transparent and colorless or it can be green. A 1970 analysis of Muzo, Colombia´s trapiche emerald by Nassau and Jackson found that the principal coloring agent was vanadium.
In Figure 1, notice the hexagonal core. This shape is typical for the growth of emeralds. Figure 2 shows a Trapiche emerald with no central core. There was some belief that Trapiche from one mining area displayed the central core and those from another did not have it. We have seen pictures on the web stating they from both localities showing with and without the core, and conversations with Trapiche dealers have suggested to us that the presence of a core or lack thereof does not indicate area of origin.
Regardless, both forms are lovely gems.
You can also let your imagination run free when you gaze upon these precious gems. In the stone below I see a spider.
And in this gem I see a moth.
Trapiche emeralds can get very large and weigh several grams:
Where do Trapiche Emeralds Come From?
It was long believed that trapiche emeralds only came from Colombia at the Muzo and Penas Blancas mines. However we have found a reference to another location: a large grayish green trapiche beryl weighing 13.74 carats from Madagascar has been reported in GIA’s Gems & Gemology publication. Information is very scarce on trapiche emeralds from this area.
Are Trapiche Emeralds Treated or Enhanced?
A quick word on treatments and enhancements is in order at this point: visitors to the actual mines recently reported obviously treated material being sold as natural. Treatment takes many forms. The most common is oil or epoxy impregnation of cracks, but this type of treatment is typical for most of the emeralds on the market.
References: All sites visited on 8 March 2015
- Author Unknown. “…and trapiche beryl.” Gems & Gemology Summer (1998): pgs 137-138
- Marc Gering, Jazzan Jewels (except where noted)
- Gems and Gemology, Winter 1999, Classifying Emerald Clarity Enhancement at the GIA Gem Trade Laboratory – by Shane F. McClure, Thomas M. Moses, Maha Tannous, and John I. Koivula, p.176-p.185.