Nestled between the towering cliffs of the Zorian plateau, lies a vast cavity that is wide enough to swallow an adult bull elephant with enough space to spare for a small herd of draft horses on either side. There you will find gold, an abundance of it. But what is that you say? That the natives tell you that it is a place of death and home to hideous monster that will devour you? Ignore the savages. They only seek to protect what they are too indolent to grab for themselves.
-A Khanate offical assuring a bunch of miners.
Orcish currency is derived from glass beads. The art of glassworking is well beyond them, but perhaps the orcs have something of value to the civilized races, such as animal pelts, and well made axes, and bows. The humans trade beads for the goods, and the orcs will trade the beads amongst themselves as a form of their own currency. Perhaps they value blood red beads above all others, or animistic orcs favor beads in the colors of their gods.
Inspired by Indian trade beads, some of which could be quite ornate and beautiful. Most North American Indian beads were made in Italy. Surprise!