I have read that cochineal (which makes a vivid red dye) whose source was jealously guarded by the Spanish was a source of great wealth, valued by weight at similar levels to silver. But I don't know what portion of the empire's wealth came from the cochineal trade. Was it moving in comparable volumes to silver or gold?
And while I'm as it, I don't really understand why cochineal was so valuable. There were other reds. Why were people willing to pay so much for this one? I've read that roman cardinals and British officers dyed their clothes in the stuff. But surely if you're the British you don't want to be financing your enemies?
While there were other reds, the red of cochineal is a force to be reckoned with. First, cochineal was specifically found in abundance in Mexico (specifically in Oaxaca),^[1] and were easy to cultivate and use. The only comparison was kermes, an insect in Europe that was largely considered a pest.^[2] As in most history, the concept of NIMBY (not in my backyard) was alive and well, and if you could get something without having to deal with it yourself, that was a huge plus. Like the silk worms of the East, European nobles, no matter their country of origin paid a lot of money for foreign goods to bring them status and beauty.
Second, while kermes produced a red, it was nothing compared to the reds of cochineal. Kermes was seen as dull and faded, cochineal was incredibly vibrant.^[3] Whether it was or not was depended on the individual dye shipment, but cochineal was exotic! Dried cochineal had been sent to Montezuma for decades as tribute by Tenochtitlan's neighboring cities. When Cortés invaded Mexico, one of the first things he wrote about was the vivid reds seen on Montezuma and nobles' robes.^[4] Those tribute bags were immediately shipped off to Spain and were in high demand soon afterwards.
Less than a century after Cortés' landing, cochineal was the second-most valuable export from Mexico except for silver.^[5] Unlike silver, which was mined to scarcity after some time, cochineal was still harvested in incredible amounts up to and through the creation of synthetic dyes in the late 19th century.
Around this time last year, I was in Oaxaca myself. The use of cochineal is still alive and well today there!