Tungsten Exploration

Among its many applications, tungsten is used in metalworking, mining, and stone-cutting tools, high-temperature technologies, lighting, catalysts, pigments, armaments, and aerospace. A list of 35 critical minerals was published by the United States Department of Interior in May 2018, including tungsten.

Primary tungsten minerals can be divided into two groups:

Wolframite group – wolframite (Fe,Mn)WO4 | hübnerite (MnWO4) | ferberite (FeWO4) | sanmartinite[(Zn,Fe)WO4]

Scheelite group – scheelite (CaWO4) | stolzite/respite (PbWO4)

Among the minerals, wolframite and scheelite are the most abundant, and they are the most economically important.

The most likely source of secondary tungsten minerals is hydrothermal alteration or supergene weathering rather than atmospheric weathering. Grey et al. (2006) reported that primary tungsten minerals, like ferberite and scheelite, may undergo hydrothermal alteration, which may result in secondary tungsten minerals, including:

  • ferritungstite [(W,Fe)(O,OH)3]
  • aluminumtungstite [(W,Al)(O,OH)3]
  • jixianite [Pb(W,Fe3+)2(O,OH)7]
  • elsmoreite [WO3·0.5H2O]
  • hydrotungstite [WO3·2H2O]
  • tungstate [WO3·H2O]
  • anthoinite [AlWO3(OH)3]
  • phyllotungstite [(CaFe3+)3H(WO4)6·10H2O]

Typical secondary tungsten minerals include hydrotungstite (WO3·2H2O), anthoinite [AlWO3(OH)3], and cerotungstite [CeW2O6(OH)3].

Supergene alteration of tungsten minerals was studied through a case study (Tarassov, M. 2018) in the Grantcharitsa scheelite deposit in Bulgaria. In this deposit, scheelite and pyrite dominate the mineralogy. Scheelite secondary minerals are known to be extremely complex under a range of pH of supergene solutions contained in the deposit’s oxidation zone.

A quick, in-situ, field solution to identifying these minerals and their alterations is to utilize a full range UV-Vis-NIR spectrometer. Important spectral features of these minerals like wolframite and scheelite can be seen.

The figure below shows the spectral data of Scheelite with distinctive absorption features occurring in the 580nm-1700nm spectral range. Geologists can use these specific features to identify scheelite in the field without the need for laboratory analysis or destruction of the sample.

Tungsten Exploration

With Spectral Evolution field portable UV-Vis-NIR spectrometers and EZ-ID™ mineral identification software, geologists can measure and identify minerals within seconds and cover more ground than by using traditional methods. They can identify different mineral phases, create mineral alteration maps and more accurately identify mineral pathfinders for vectoring to ore deposits. Spectral Evolution’s field portable, battery-operated oreXpress™, oreXplorer™ and oreXpert™ ultra-high resolution UV-Vis-NIR spectrometers provide quick payback with faster, more accurate mineral identification in exploration for gold, silver, diamonds, iron, nickel, copper, uranium, aluminum – in the field, core shack, or in the lab.