Final answer:
Historically important ruby and sapphire occurrences are mainly found in Burma's Valley of Rubies, with most gems sold in Thailand. Rubies owe their color to chromium impurities. The lack of disclosure of gemstone treatments often leads to asymmetric information in the market.
Step-by-step explanation:
The historically important ruby and sapphire occurrences can be chiefly attributed to regions in Burma (Myanmar) known for producing around 90 percent of the world's rubies. The famed Valley of Rubies is renowned for its high-quality gem production with most of the stones being sold in Thailand. It is crucial to acknowledge that rubies as allochromatic minerals owe their color to the presence of traces of chromium impurities (Cr³+) within an otherwise colorless metal oxide lattice.
This detail is central to understanding the intrinsic beauty and value of these gems. Rubies and sapphires are subjected to various treatments to enhance their appearance; however, disclosure of such treatments is often lacking, leading to asymmetric information within the gem market. This practice affects the economic transaction between sellers and buyers, underscoring the necessity for transparency within the gemstone industry.