After recovering just 12 diamonds from 2,400 cubic metres of gravel from the Barra Grande alluvial diamond project in Brazil’s Minais Gerais state, Trans Hex International (THI-V) has decided to stop funding the project and resign operatorship once the current exploration program wraps up.
The gravel sample represents an eight-metre thick intermediate gravel horizon at the northern sampling site. The sample returned an average grade of 0.1 carat per 100 cubic metres. The average stone size was 0.2 carat.
Last month, a total of 2,045 cubic metres of basal gravel yielded just on diamond weighing in at 0.45 carat.
Barra Grande is an alluvial diamond project that covers 62,500 ha along the banks and terraces of the Rio Grande river, between Sao Paulo and Minas Gerais states. Sampling has been ongoing on the property since February.
In September, results from the first trench on the Villa Barroso target (the southernmost of the three) were not encouraging. All the recovered stones were gem-quality and reasonably large in size, but the commercial valuation produced results that were below expectations.
The gravels consist of three discernible units; a 2-metre basal unit of well-sorted and rounded clasts in a matrix of clay, followed by a middle unit of coarser pebble gravel measuring 2 metres where most of the diamonds were found. The uppermost unit of coarse gravel measures three metres in thickness.
In all, 28 diamonds were found in the middle unit, totalling 14.9 carats, in more than 2,400 cubic metres. However, the valuation came out at US$200-250 per carat, about half Trans Hex’s average sale price per carat on current production in South Africa.
At the end of September, Trans Hex had an effective 63.4% interest in a joint venture with partner Verena Minerals (YVM-V).
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