Search

The article discusses the gemological properties of five faceted samples of sphenes from Afghanistan that were donated to the Gemological Institute of America (GIA) for examination. Gemological testing revealed a brownish yellow to greenish yellow color, a strong with predominantly red and green flashes of dispersion, a hydrostatic specific gravity of 3.53-3.54, and a weak pink Chelsea filter. Energy-dispersive X-ray fluorescence (EDXRF) spectroscopy of three of the samples indicated silicon, calcium and titanium.

The article discusses the gemological properties of six faceted uvite-dravite tourmalines that were loaned to the Gemological Institute of America (GIA). The specimens exhibited a brownish orange, brown-yellow, orangy yellow, brownish yellowish green and yellowish green colors, with one stone appearing bicolored in yellow-green and reddish brown due to its cut revealing strong pleochroism face-up. The stones showed a birefringence of 0.019-0.021, a hydrostatic specific gravity of 3.05-3.07 and a fluorescence of long-wave ultraviolet (UV) radiation.

The article discusses the gemological properties of some rough and cut examples of lime green herderite that were loaned to the Gemological Institute of America (GIA) for identification. The two faceted herderites showed weak-to-moderate green and yellowish green pleochroism, a transparent diaphaneity, refractive indices of 1.587-1.616 and 1.586-1.616, birefringence of 0.029 and 0.030, hydrostatic specific gravity of 3.02 and 3.04, and a weak-to-moderate blue and moderate-to-strong blue to long wave ultraviolet (UV) radiation. Microscopic examination of both samples revealed moderate-to-strong doubling and numerous partially healed fractures with negative crystals.

The article describes a selection of sphene from Pakistan featured by Dudley Blauwet at the American Gem Trade Association (AGTA) show. The stones were initially obtained in mid-2004 which reportedly came from a mining area called Mulla Ghani Baba. The stones are a saturated golden orange color with intense dispersion with red flash. It ranges from yellow to orange-brown, with greenish brown and greenish yellow colors seen less commonly. Some samples were loaned and donated to the Gemological Institute of America (GIA) for examination. Energy-Dispersive X-Ray Fluorescence (EDXRF) spectroscopy revealed a combination of silicon, calcium and titanium in the samples, along with varying amounts of iron, niobium, yttrium, zirconium and strontium.

The article describes a transparent faceted sillimanite discovered in the Vishakhapatnam region of Andra Pradesh, India presented at the American Gem Trade Association (AGTA) show by Anil B. Dholakia Inc. The stones all have checkerboard cuts with various colors ranging from greenish yellow, near colorless, grayish green, green-brown, brownish orange-yellow and violetish gray. Several samples were examined by the Gemological Institute of America (GIA). Three largest stones were selected which are of yellow-green and yellow and grayish green in color. Based on microscopic examination, the two yellow-green stones contained parallel iridescent needles while the greenish yellow stone contained fine whitish parallel needles.

The article describes pyrope-spessartine garnets from Tanzania. The stones are marketed as Imperial garnet and have been in production since late 2005 from Lindi Province in Madagascar. The stones were presented by Steve Ulatowski on New Era Gems at the 2006 Pueblo Gems & Mineral Show in Tucson, Arizona. He claimed that the stone is quite rare and the largest stone with good clarity. A sample cut was examined by the Gemological Institute of America (GIA) and revealed that the stone was pink in color in both incandescent and daylight but brownish pinkisho range in fluorescent. Iridescent needles, subhedral transparent bifringent crystals nad dust-like particles were shown by microscopic examination.

The article discusses the gemological properties of a glass imitation of alexandrite being sold a Zandrite and donated to the Gemological Institute of America's (GIA) collection by Samuel Gullo of Tsavo Gem Imports for examination. The sample's refractive index was 1.538 and its hydrostatic specific gravity was 2.82. The blue-to purple sample showed weak anomalous double refraction and a very weak orangy pink Chelsea filter reaction, and was inert to both long- and short-wave ultraviolet (UV) radiation. Energy-dispersive X-ray fluorescence (EDXRF) spectroscopy found silicon as a major constituent, and trace amounts of potassium, copper, zinc, zirconium, cerium, and neodymium.

The article discusses the gemological properties of six samples of albitic moonstones from the Morogoro region in Tanzania, examined by the Gemological Institute of America (GIA). The samples, consisting of five cabochons and one cushion mixed cut ranging from 5.44 to 19.88 carats yielded very light gray to very light yellow, with strong adularescence, transparent to semitransparent diapheneity and refractive index of 1.530 to 1.540 from the faceted stone. Birefringence was at 0.010 and specific gravity was at 2.64. The stones were inert to long-wave ultraviolet (UV) radiation and a weak red reaction to short-wave, and no absorption lines were visible with the desk-model spectroscope.

The article discusses the gemological properties of a 1.11 carat faceted pezzottaite from Afghanistan that was donated to the Gemological Institute of America (GIA) . The sample had a birefringence of 0.007 and a specific gravity of 2.97. Its diapheneity resulted to transparent to semitransparent, while its fluorescence exhibited a very weak violet to long-wave ultraviolet (UV), and a weak banded white to short-wave. Chemical analyses of this 1.11 ct stone by electron microprobe confirmed its identity as pezzottaite.

The article discusses the gemological properties of a sillimanite that was donated to the Gemological Institute of America (GIA). The 6.65 carat oval specimen showed an unusual blue-white sheen when strongly illuminated in certain orientations. It exhibited a light gray color, a transparent diaphaneity, a refractive index of 1.661-1.680, a birefringence of 0.019, and hydrostatic specific gravity of 3.26. No absorption features were observed with a desk-model spectroscope. Microscopic examination revealed that the stone contained two-phase inclusions and numerous fine, parallel, whitish needles.

The article presents an update on the gem-quality prehnites that were mined from Mali. In December 2005, mining for prehnite and associated minerals at several localities in the country had become prevalent. Several types of minerals have become available in the market in Bamako, Mali's capital, with prehnite and garnet being dominant. The prehnite is mined from a rather small area centered around Bendoukou village wherein the deposits are associated with localized diabase intrusions. Four polished samples of mined prehnites were donated to the Gemological Institute of America (GIA) for examination.