Aquamarine General information
In the beryl species, aquamarine is second only to emerald in popularity. Fine aquamarines are paired with diamonds and mounted in platinum in this jewelry suite.
The name “aquamarine” is derived from two Latin words: aqua, meaning “water” and marina, meaning “of the sea.”
In the commercial market, aquamarine competes with treated blue topaz for attention, but fine aquamarine sells for far more than equivalent-quality treated blue topaz. In early 2012, wholesale prices for a good quality African origin 3-ct size stone ranged from $65 to $120 per carat depending on the degree of color saturation.
Aquamarine’s hardness and transparency make it popular with designers, artists, and carvers. Gem sculptors use aquamarine for fantasy cuts and ornamental objects.
Aquamarine’s color range is very narrow: It can be blue, very slightly greenish blue, greenish blue, very strongly greenish blue, or green-blue.
Although sapphire is the most popular blue gemstone, aquamarine is one of many other blue stones that have considerable markets of their own. Even in its darkest shades, however, aquamarine rarely matches sapphire’s blue.
Like most beryls, well-formed aquamarine crystals are typically six-sided columns with flat faces at their ends.
Cutters align the table facet parallel to the length of the crystal. The gem is pleochroic, showing near-colorless and strong blue in different crystal directions. Fortunately, the blue pleochroic color coincides with the cutting orientation that retains the most weight. Cutters often fashion aquamarines as emerald cuts or as round or oval brilliants. The rough is fairly plentiful, so well cut stones are usually available. Aquamarine crystals can range from very small to very large-up to 100 lbs. (45 kg) in some cases. Large stones are readily available, but it’s difficult to use very large stones in jewelry, so there’s less demand for them. As a result, per-carat prices tend to decrease for sizes above 25 cts.
Fashioned aquamarines often have to be fairly large-generally over 5 cts.-to show intense, dark color. Although small gems are rarely saturated enough to be attractive, stones from some mines in Africa-Nigeria, Madagascar, and Mozambique, for example-are known for intense color in sizes under 5 cts. For this reason, smaller, top-color stones might sell for more per carat than larger stones of the same color.
Most faceted aquamarines are eye-clean. Some crystals might contain liquid inclusions, but clarity characteristics are few or absent in most finished gems.
Aquamarine imitations and synthetics
Russian growers produce hydrothermal synthetic aquamarine, but it’s not widely available. The most common aquamarine imitations are treated blue topaz, pale blue glass, synthetic blue spinel colored by cobalt.
Separating natural aquamarine from all other imitation can be fairly easy. Standard gemological test like refractive index, and Chelsea filter easily distinguish aquamarine from its imitators.
Today’s Aquamarine sources and market
Brazil has been the world’s most important source of gem-quality aquamarine since 1811, when a miner found a large aquamarine crystal in a riverbed near Teofilo Otoni. It weighed about 15 lbs. (7 kg), and it was the first large aquamarine crystal ever recorded. Millions of carats of fine aquamarine have been found in the thousands of mines throughout the region.The largest aquamarine crystal on record was found in 1910, in Minas Gerais, Brazil. 244 lbs. (110 kg) 19 in. (48 cm) long and 15 in. (38 cm) in diameter
Although the fine blue-green crystal was water-worn, most of it was gem-quality, and so transparent that people were able to read printed pages through the length of the crystal.
When German immigrants settled in Brazil about 1850, they discovered that they could dig almost anywhere, with almost any kind of equipment, and turn up aquamarine crystals. Someone sent samples to Idar-Oberstein, Germany-then, as now, an important cutting center-for examination. That was the beginning of a close gemstone mining and marketing relationship between Brazilian miners and German cutters.
Most aquamarine mines are located in northeast Minas Gerais. Although some darker crystals come directly from pegmatite, alluvial deposits yield most material. Historically, aquamarine and other gems have been found in riverbeds or have been dug out of the ground by independent miners called garimpeiros. Because new laws make it hard for garimpeiros to operate, the recovery method has switched to mechanized strip mining.
There are no accurate production figures for Brazilian gems because no official records are kept. Trade sources estimate, however, that less than 5 percent of the yield from Minas Gerais consists of top-quality, dark blue stones.
Pakistan is another significant producer of aquamarine. Pegmatites produce light green and blue crystals, some up to 12 in. (30 cm) long by 5 in. (12 cm) wide. Miners also find inky blue crystals.
China recently became the world’s leading producer of small, commercial-quality aquamarine. Most of the stones measure about 6×4 mm, and commercial-grade sizes rarely exceed 10×8 mm, or about 2 cts. Crude mining techniques damage many crystals, and yield of gem-quality crystals is only between 10 percent and 15 percent. Some trade members say that if Chinese miners were more careful, they could produce bigger stones with deeper color.
Chinese aquamarine has replaced Brazilian material in most of the mass-marketed jewelry available through home-shopping networks and other high-volume outlets.
The introduction of treated blue topaz in the 1980s had a negative effect on the aquamarine market in the United States, but not elsewhere. Consumers in Japan and Europe preferred aquamarine, and were prepared to pay high prices for top-quality gems.
In the late 1990s, Japan was the best market for high-quality aquamarine. Medium to high-quality stones also sold well in Germany and Italy, and almost all grades were marketable in the US.
Nigeria is known to be source of aquamarine that produces large and clean material since the beginning of 1990s. Generally speaking, most of the characteristic colors of Nigerian aquamarine are light greenish blue to blue and fairly uniform in color. This makes them favorable amongst many TV shopping networks producing mass-market silver jewelry.
Mozambique and Madagascar
Deposits of Madagascar and Mozambique are the most recent discovery of high-quality aquamarine of dark colors has been unearthed. Material in Mozambique can possess a particularly rich blue hue cut aquamarine is a real treasure from this area.
From Mozambique “Santa Maria color” Aqua has a very fine natural blue. In addition, it has been distinguished from aquamarine from other localities by the ability to hold strong color even in small stone. Rich pegmatites pocket that contain gems of beryl is prevalent and spread throughout African continent. It seems to me that not long enough, we will expect to see more aquamarine production from many parts of Africa.
Less significant sources are Australia, Kenya, the US, and Zambia.
Virtually all of the blue color in aquamarine derived from heat treatment of bluish green, greenish yellow, or even brownish yellow gems. Control Heating process can remove the yellow color component and leaves a purer blue hue to the stone.
It’s standard practice to cut the rough and then heat the fashioned stones. Because aquamarines are largely free of liquid inclusions, they respond well to heat treatment. Depending on the source mine and the stones’ clarity, treaters heat aquamarine to between 482ÂºF and 1,292ÂºF (250ÂºC and 700ÂºC) for varying lengths of time. Treaters heat stones with significant inclusions for longer periods, at lower temperatures. In most cases heat treatment in aquamarine cannot be detected and treated color appears to be permanent.
Some dealers, however, leave greenish blue aquamarine untreated and use its uniqueness to promote it. Its untreated color sets it apart from its competitor, treated blue topaz. Some dealers see blue topaz’s saturated market as a sign of good times ahead for aquamarine. And because of current widespread concern about treatments, untreated gems-like natural-color aquamarine-appeal to more consumers than ever before.
Source by Napat Boonta