The following commentary comes from an independent investor or market observer as part of TheStreet's guest contributor program, which is separate from the company's news coverage. NEW YORK ( Trefis) -- Vale ( VALE) recently discovered a rich deposit of rare minerals (also called rare earths) at its Salobo copper mine in Carajas, Brazil. China's restrictions on the export of rare earth minerals has made this discovery even more valuable. Vale, the world's largest iron ore mining company, derives almost 20 percent of its value from its nickel business. It competes internationally with other global mining giants like Rio Tinto ( RIO) and BHP Billiton ( BHP). See our complete analysis for Vale here . Rare earth metals are high-worth minerals with applications in oil refining and microchips. China, the world's largest exporter of rare earth minerals, enforced a ban on rare earth exports to safeguard its domestic inventory. Vale started exploration for rare earth minerals in the Amazon region earlier this year after an invitation from the Brazilian President Dilma Rousseff. Rare earth mineral deposits are difficult to find in quantities large enough to make it economically viable to mine. Vale's discovery in the Salobo region where the company is already developing its copper mining operations with an investment of $2.3 billion will allow these minerals to be mined as a by-product of the copper mining operations. Prices of certain heavy rare earth metals doubled in May after China enforced restrictions on the exports. This signifies the demand-supply imbalance and the opportunity that Vale has in mining these minerals. We have a $34 price estimate for Vale , which is significantly above the current market price. Like our charts? Embed them in your own posts using the Trefis Wordpress Plugin.