It took 10,000 snails to make a single gram of dye, making it extremely expensive. At its peak, so-called Tyrian purple was worth more than its weight in gold. Some Roman emperors even passed laws ...

An incredibly rare Roman-era object—made from a substance ... pigment that was highly valued in the ancient world. The dye, which is purple in color, is secreted by several species of predatory ...

One reader wonders: Since purple dye was scarce, why didn’t people just combine blue and red? Illustration by Aurélia Fronty Q: I’ve heard that purple was called the royal color because ...