Usage examples (34)

• Rhenium is obtained almost exclusively as a by-product of the processing of a special type of copper deposit known as a porphyry copper deposit.
• The principal measured reserves are in the so-called porphyry coppers of the United States and Chile.
• The porphyry, which is of warm brown or chocolate colour, includes many crystals of lighter coloured felspar, and dark crystals of hornblende.
• The so-called porphyry copper mines, which now produce more than half the world's copper, are worth looking at in the context of exploitation limits.