Fall 2009

Preliminary Observations on New Rubies from Mozambique

GIA recently examined two groups of transparent faceted rubies that were represented as coming from new localities in Mozambique. The first group of five rubies (2.03–2.73 ct) was brought to us in May 2009 by J. Blue Sheppard of Millennium Inc., Pala, California. These were represented to Mr. Sheppard as being from “Lusingha,” and having been heated to “driveout the silk.” The locality was subsequently identified as the Lichinga area, near the village of Msawizi (or M’sawize), in Mavango District, Niassa Province, northcentral Mozambique. The second group of 19 rubies (0.70–4.62 ct) was supplied in July 2009 by Tommy Wu of Shire Trading Ltd., Hong Kong. These stones were reportedly unheated, and consisted of a mixture of those from Lichinga and a newer mine reported to be in the Montepuez area of Cabo Delgado Province, ~225 km north of Nampula in northeastern Mozambique.

GIA examined all 24 rubies by standard gemological methods and EDXRF spectroscopy. The stones from both localities were similar in visual appearance as well as gemological properties. Their color was primarily red to purplish red, with none of the orangy component that is commonly seen in many other African rubies. The stones Mr. Wu provided did not show any evidence of heat treatment when examined with the microscope and analyzed by FTIR spectroscopy. Chemical analysis by EDXRF revealed iron contents ranging from 0.09 to 0.31 wt.% Fe2O3, with an average value of ~0.16 wt.%. Also present was 0.13–0.76 wt.% Cr2O3 and minute traces of Ti, Ga, and V.

The inclusion scenes in these stones showed some of the features noted in rubies from other East African localities, but in combinations that made them somewhat different in our experience. Most were fairly included. Strong laminated twinning with networks of intersection tubules were common. Some tubules were naturally stained orange with what appeared to be epigenetic iron compounds. Dense clouds of reflective platelets, similar to those seen in sapphires from Umba, Tanzania, were present in many of the rubies. Within some of the clouds were needle-like inclusions that appeared to be rutile. A few stones also contained clouds that had a more particulate appearance. In addition, dense particulate planar clouds were seen in some samples.

Perhaps the most interesting inclusions we noted—in two stones—were rounded blue-gray to grayish blue transparent crystals that gave a Raman signal of an amphibole very close to that of pargasite. Their visual appearance was identical to the pargasite crystals found in rubies from Winza in Tanzania. It is unclear if this is a coincidence or represents contamination with Winza material. However, the inclusions in the other stones in this sample set did not resemble those documented in rubies from Winza.

Shane F. McClure and John I. Koivula
GIA Laboratory, Carlsbad