| The role of the Spanish and Portuguese was to provide wolfram using that hard currency or gold. |
| The same year Lodygin's electric lamps were illuminating a St Petersburg shop and he went on to patent the wolfram filament lamp. |
| It currently holds 20 concessions covering about 1000 square kilometres and produce mostly cassiterite, coltan and wolfram. |
| Mining remains a marginal activity, contributing about 1 per cent to GDP from three dominant products: cassiterite, coltan and wolfram. |
| These oxides are commonly met with in samples of wolfram and tinstone, especially niobic. |
| This may be obtained by decomposing wolfram with aqua regia, and evaporating to dryness. |
