Mwajanga diggings, Simanjiro District, Manyara Region, Tanzaniai

Regional Level Types
Mwajanga diggings	Diggings
Simanjiro District	District
Manyara Region	Region
Tanzania	Country

The deposit of tourmaline was discovered in 2014 near Mwajanga village, in the Komolo area of the Manyara Region of north-eastern Tanzania. The initial production - some of which was shown at the East Coast Gem, Mineral & Fossil Show in Springfield, Massachusetts, USA, in August 2014 - consisted mostly of pale yellowto-colourless crystals with pale brown, blue and pink areas (Polityka, 2014). Crystals up to 10 cm long were available, and although they were well formed, they tended to have dull lustre. In addition, only small areas were transparent enough for faceting. Further production from Mwajanga in 2014 yielded deeper yellowish-to-orangey brown (e.g. Figure 24a) and pale green crystals, some of which were quite gemmy and possessed high lustre; they have been referred to as dravite (Moore, 2014). Some of the brown crystals contained sharply defined white chatoyant zones, or displayed evidence of multiple breakage and regrowth events, producing the appearance of bent crystals. Such tourmalines were seen by author BML at the February 2015 Tucson gem shows, with rough stone dealers Steve Ulatowski (New Era Gems, Grass Valley, California, USA) and Farooq Hashmi/Michael Puerta (Intimate Gems, Glen Cove, New York, USA). Also on display were colourless prismatic crystals of natrolite up to nearly 4 cm long that reportedly were found at the same deposit as the tourmaline. Additional production in March 2015 consisted of multicoloured tourmaline crystals that ranged from black to orangey brown, yellowish green and bright pink.

Most of the Mwajanga tourmaline has been sold as crystals to mineral collectors, and until recently these authors were unaware of any faceted material. However, in July 2016 gem dealer Dudley Blauwet had some pale brownish yellow and greenish brown faceted gems that ranged from 0.20 to 0.82 ct. The 42 stones (17.43 carats) were cut from 36 pieces weighing a total of 15.1 g. He obtained the rough material during the February 2016 Tucson gem shows from a stone dealer who purchased the tourmaline in Mwajanga. The rough consisted mostly of gem nodules, as well as some 'fawless' complexly formed crystals.

Blauwet loaned four of the cut stones for examination (Figure 25), and authors AUF and WBS performed standard-based SEM-EDS chemical analysis using a Jeol JSM-6400 instrument with the Iridium Ultra software package by IXRF Systems Inc. The results showed that all four samples had a very similar composition that consisted of dravite with a minor uvite component (0,90-0,96 wt.% CaO). Consistent with the pale coloration, there were few minor and trace elements; MnO and FeO were present in very low amounts (0,01-0,02 wt.%), V2O3 was only slightly above the detection limit (0,01 wt.%) and TiO2 and Cr2O3 were not detectable [Laurs, Brendan M.; Falster, Alexander U.; Simmons, William 'Skip' B. The Journal of Gemmology. 2017].

Jochen Hintze (dealer) say about Mwajanga: "It is not really a village but a mining area about 15 km far from the masai village of Komolo. There are several hills full of so called foxhole mining. All pockets are bound to a metamorphic dolomite, and at the beginning of mining tourmalines were found in and with natrolite crystals, now the tourmalines are found in calcite."

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