Book 37 Chapter 21 Opals: seven varieties of them.
Chapter 21 opals seven varieties of them describe opals and their origin. Pliny describes the different colors of opals and their routes. Pliny states that opal originates in India and that is where the Romans had procured it. These two items are different kinds of opals. Within the chapter, Pliny describes the great price of opals and the wealthy that owned rings of opal.
Pliny's chapter on opals is important as it offers an intersection of the value of luxury goods as well as the result of imperialism. Opals originate in India so for the Romans to have acquired opal trade with India was necessary as well as a market for opal between the two created. Imperialism between provinces emerged during this era. Pliny feels it important to understand the origin of opal, as it indicates imperialism.