Diamonds (and rumours of their existence) are not new in Mozambique since colonial times (DIAMANG’s DIAMOC subsidiary had some activity in Mozambique). Later on, kimberlite were discovered/confirmed by soviet teams in the (then already independent) country.
Until now, the country has seen no industrial diamond production (or large scale diamond garimpo activity). That is perhaps about to change. Mustang Resources Limited (an Australian company) has just announced the discovery of alluvial diamonds in the gravels of their concessions along the Save River, in southwestern Mozambique. You may read the full news releases here: Mustang Discovers Diamonds – JORC Table 1 (June 16, 2015), Mustang Discovers Diamonds in Mozambique (June 15, 2015) and their previous (June 10, 2015) Save River Diamonds Project Update; the company’s October 2014 presentation in OGIGROUPLTD PROJECTS_28Oct. Or, if rather prefer, at ASX website.
Mustang Resources Limited (ASX:MUS), formally called OGI Group Limited, is an ASX listed company focussing on diamond and graphite exploration and mining in Mozambique. You may refer to company’s website for further info on the project: http://mustangresources.com.au/mozambique-overview/diamond-project/; I also suggest you read the details of the information and comments about sampling and geological models included in Mustang Discovers Diamonds – JORC Table 1 (especially the last pages of the document).
Results and my comments (both very preliminary; the comments, of course, subjective)
16 diamonds (classified as gems) were recovered from 5 pits (9.68 ct with an average stone size of 0,60 ct/stone in a total of 4.732 m3).
It is a very early stage; it is a success to find diamonds in the first tests. Nonetheless, overall grade is small and stone size good (please note, these are preliminary results and they may not be considered representative of the potential mineralization contained in the gravels).
The company is using a rotary pan as a concentration process. Although extensively used in South African gravel fields, I would rather use a DMS small scale plant (or a jig based system).
The Save River Diamonds Project is located in southern Mozambique, next to the border with Zimbabwe. The area of interest is along the Save River, after the confluence with the Runde River.
The licence areas are located where gravels, conglomerates and grits have been mapped on the surface. The tertiary to quaternary aged sediments are potentially associated with alluvial diamonds.
Metallogenical model (summary)
The geological model for this project is based on the Save and Runde Rivers having drained areas some 200 kms upstream with rich diamondiferous conglomerates and kimberlites (Murowa and Marange diamond fields in Zimbabwe) over millions of years.
The profile of the Save/Runde Rivers from the Marange/Murowa areas in Zimbabwe to the Save River Diamonds Project shows a very steep gradient resulting in a high energy environment which the Save River maintains until it reaches the confluence with the Runde River. The topography then changes to a gentle and almost flat surface at the confluence of the rivers. This has resulted in a massive deposition of gravels on the concession area which is a substantial 40km x 10km in size.