Tether Holdings Ltd. is trying to convince Turkey to use digital assets to overhaul the country's boron market, in the latest sign that the backbone of the cryptocurrency industry is trying to leverage the commodities sector for further growth. Tether, the issuer of stablecoins, has presented a proposal to government officials to create digital tokens representing borate minerals using blockchain technology, according to people familiar with the matter. Tether has also floated the idea of setting up a digital asset exchange in Istanbul. A Turkish government official said the boron proposal cannot be implemented at this time, while an official from Turkey's energy ministry said talks with Tether are still at an early stage.