Aquapraseis a newly discovered gemstone variety of chalcedony with vibrant bluish-green color and comes from a non-disclosed location in Africa.
The translucent material displayed a vibrant bluish green color and is currently marketed under the τɾɑԀє name “Aquaprase.” Although chalcedony varieties such as chrysoprase and Gem Silica are well known and occur in yellowish green and greenish blue colors, the color of this material was distinctly different from any African chalcedony examined by GIA to date.
One of the most distinct features of blue chalcedony is its colour. As it comes from the quartz family, the two closest gemstones it can be compared to are chrysocolla (turquoise in colour with a forest to light green shade when associated with malachite) and chrysoprase (yellow-green). Compared to those two, the colour of aquaprase is more pleasing to the eye and is already a favourite of those who have worked with it.
This new gem has a distinct lagoon turquoise colour that is pleasing to the eye.
Photo:Kenilworth Media Inc.
From a gemmological point of view, aquaprase contains unusual amounts of moganite (not to be confused with the peach-coloured gem, morganite). It has the same chemical composition as quartz, but with a different type of crystallization in the growth of the gemstone. (Research was conducted to distinguish moganite from quartz in 1994, but the two gemstones had so few differences, the research team decided moganite should be a quartz. Ergo, aquaprase is in the quartz family.) The gemstone was discovered somewhere in Africa, with the exact location remaining a secret for the moment.
As for the components causing the colour,aquapraseis composed of minerals including chromium, nickel, and iron. It contains far more minerals than its sisters—the colour in chrysocolla is caused by copper, and nickel gives chrysoprase its colour.
Figure 2. A large piece of chalcedony ɾօυɢҺ recovered from the mining area. Photo by Yianni Melas.
From a gemological perspective, it was important to conclusively determine that this material was naturally colored and not artificially dyed. Since the quartz crystals present in this material were colorless rather than brown, we ruled irradiation out as a possible treatment. Microscopic examination of ɾօυɢҺ and cut stones in conjunction with chemical analysis and visible spectroscopy were used to characterize this chalcedony.
Standard gemological testing ɾєⱱєɑłєԀ an RI range from 1.531 to 1.539, with no observable birefringence. The SG, measured hydrostatically, ranged from 2.55 to 2.57.
A handheld spectroscope ɾєⱱєɑłєԀ faint, narrow lines in the red єɴԀ of the spectrum, rather than the broadband absorption one would expect if the material had been dyed with an organic pigment. All of these features were consistent with natural-color chalcedony.
Microscopic examination ɾєⱱєɑłєԀ a granular aggregate structure with a few areas showing subtle banding and faint green concentrations of color between some of the coarser quartz grains, which appeared to be a greenish mineral phase located along the grain boundaries.
A waxy luster was observed on fractured areas, consistent with an aggregate material. Some areas contained small cavities that were filled with colorless drusy quartz crystals.
Dark brown and black inclusions of various metal oxides were also observed scattered thɾօυɢҺout most of the samples examined, along with some areas of whitish cloudy inclusions that were not identified
This new type of African chalcedony is easily recognized by its unique composition and absorption spectrum, which is significantly different from the chrysoprase and Gem Silica varieties.
The attractive bluish green color of Aquaprase, which may be caused by chromium and nickel, should prove to be a popular and welcome addition to the gem τɾɑԀє.
