Noventa (LON:NVTA) has reported that a Glasgow University project, which included extensive mineralogical, textural and chemical work, indicates that “some simple and low-cost measures have a significant impact on improving tantalum recovery levels” at the Marropino tantalum mine in Mozambique.
The company has been working with a team from the University of Glasgow, to independently examine Marropino’s mined ore to identify opportunities to improve tantalum recovery levels. Separately, the standard mineralogical investigative and test work commissioned by Noventa has reached similar conclusions, which has increased confidence in the improvements and upgrades planned at Marropino.
Historically, whilst under previous management, Marropino’s tantalum recovery was relatively poor. According to Noventa, less than half of the tantalum contained within ore was typically being recovered, with the remaining half left in waste dumps, or lost during processing.
The company highlighted that the reasons behind the low recovery were not entirely clear, and merited detailed investigation and verification before moving forward.
“One hypothesis was that much of the tantalum bearing ores was locked within grains of other minerals, and thus could not be separated or extracted. Flakes of mica were suspected of retaining tantalum mineral grains and preventing recovery. Micas are problematic to process. Another suspicion was that there might be significant ultrafine-grained tantalum minerals which would be difficult, or impossible to process, despite the apparent richness of the ore”, Noventa stated.
The Glasgow University project investigated the distribution and textural relationships of tantalum-rich mineral grains in the Marropino ores, and examined ways to improve processing efficiency. The project’s findings suggest that simply reducing ore to a slightly finer fraction size (< 1mm) demonstrated the liberation of significantly higher levels of the tantalum-bearing grains for processing.
“Critically for this process, mica crystals do not seem to include many tantalum-rich grains, and thus removing mica early in process also improves efficiency with only marginal loss of tantalum. It has also been shown that very little of the tantalum within the ores appears to occur as ultrafine grains”.
According to Noventa, the Glasgow University project implies that simple adjustments to existing technologies may provide big improvements in recovery. Furthermore, these processes should also be applicable to the extensive tailings dumps at Marropino. Noventa highlighted that these discarded waste-dumps from earlier mining, still contain significant quantities of tantalum.
Additionally, the company noted that, in a related project, geology students from Glasgow and Mozambique will be working with Noventa, to assist fieldwork teams during summer 2010. This fieldwork will provide improved mapping of exploration licence areas held by Noventa's subsidiary HAMC Limitada in Mozambique.
The Marropino mine was restarted in late April, after being placed on care and maintenance in May 2008. In October 2009, Noventa declared it was mulling all options regarding the asset, subsequently deciding to reopen Marropino due to the positive medium term outlook for tantalum demand.
Noventa is looking to capitalise on the demand for tantalum which is used in the manufacturing of capacitors for mobile phones, motherboards and audio and video equipment and which the company said was projected to outstrip supply in 2010 and 2011, while the production of microelectronic goods was projected to increase.