Assignment 15 - Emerald Flashcards
What is emerald’s most important value factor?
Color.
How are emerald colors commonly described in the trade?
“Colombian” is commonly used to describe the finest emerald color—a color that matches the best stones from Colombia, which are slightly bluish green with medium to medium-dark tone and strong to vivid
saturation.
“Zambian” is often used to describe emeralds that are slightly darker and more bluish than Colombian emeralds, and often have higher clarity.
“Sandawana” describes emeralds that match stones from that source, which are commonly a bright, intense green, even in small sizes. The source itself is no longer producing, but the stones are still present in the market.
What conditions exist in places where emeralds form?
Most emeralds are mined in regions with metamorphic-rock environments, where pegmatites intersect with schists.
What properties influence the cut of an emerald?
One challenge is the bluish green to yellowish green dichroism of many emerald crystals. If the cutter orients the table perpendicular to the crystal’s length, the cut gem’s face-up color is the bluish green prized by most emerald lovers.
Even if they’re not prominent, multiple inclusions can affect the brightness of some stones and make them appear dull. Also, emerald’s color zoning must be considered when the most intense color is located close to the crystal’s surface. Trying to remove or conceal clarity characteristics while also accommodating surface-related color zoning adds a significant level of difficulty for a cutter whose goal is the best possible face-up appearance.
How does emerald clarity relate to its value?
Inclusions that reduce transparency or that are highly visible can have a strong negative effect on emerald value.
What are the principal treatments applied to emeralds?
Emerald’s fractures are often filled with oil or resin or a mixture of both.
What are the advantages and disadvantages of oils vs. resin fillers?
While oils are not soluble in water, they are vulnerable to alcohol, household cleaners, and other solvents, as well as to heat, light exposure, and drying conditions. Over time, some
oils can become visible as a brown, white, or yellowish green residue.
Heat from a bench jeweler’s torch can cause oil to sweat out of surface-reaching fractures and leave tiny beads on the stone’s surface.
Resins have the advantage of higher RIs and less vulnerability to solvents.
How does the GIA Lab classify fracture filling in emeralds?
The GIA Laboratory uses a system ranging from “no indications of clarity enhancement” through “clarity enhanced” at minor, moderate, or significant (stated as F1, F2, and F3) levels. The lab uses the classification system only to evaluate the overall effect of the treatment, not to evaluate an
individual stone’s clarity.
Where are the principal sources of emeralds?
Emerald is mined primarily from hard- rock sources rather than secondary ones.
Colombia, Zambia, Brazil, and the Central Asian countries of Afghanistan and Pakistan supply the great majority of emeralds on the international market.
How do exploration and mining techniques vary from source to source?
In Colombia, modern mechanized mining of emerald by private companies began in 1977. Blasting extends the mine tunnels while hand picks are used to carefully remove the emeralds.Government geological surveys suggest that only 20 percent of Colombia’s emerald reserves have been mined.
Zambia’s Kagem mine produces an estimated 20 percent of the world’s emerald supply. Gemfields uses a strip and fill process, stripping ore from one end of the pit, called the highwall,
and using it to fill in the opposite end, called the footwall.
What routes do emeralds follow from the mines to retailers?
Jaipur, India, is the global leader in the cutting of Zambian emeralds.
Colombia and Brazil cut most of their better-quality emerald rough and send the lower-quality material to Jaipur, India.
India is the number one supplier of emerald to the US in terms of total carats, while Colombia is number one in total value.
Switzerland is the number one
exporter of emerald to the US in terms of per-carat price.
What materials can be used as emerald imitations?
Some of them are quench-crackled and dyed quartz, synthetic spinel triplets, green synthetic cubic zirconia (CZ), green yttrium aluminum garnet (YAG), and beryl triplets that consist of two pieces of colorless beryl glued together with green cement. Light-colored beryl might also be dyed for use as an emerald imitation.
What methods do manufacturers use to make synthetic emeralds?
Today, hydrothermal is the primary synthetic emerald growth method.
What are some characteristics of emerald imitations and synthetics?
Generally, synthetic
emeralds have fewer fractures and higher clarity than natural emeralds.
Brazilian emeralds are mined from
A.
limestone.
B.
hydrothermal deposits.
C.
solidified volcanic magma.
D.
areas where pegmatites intersect with schists.
D.
areas where pegmatites intersect with schists.
To emphasize the bluish green color, cutters orient a fashioned emerald with its table
A. parallel to the crystal length.
B. perpendicular to the crystal length.
C. at a 45° angle to the crystal length.
D. at a 30° angle to the crystal length.
B. perpendicular to the crystal length.
