The island of Sri Lanka, also known as Ratna Dipa (Island of Gems), boasts a legacy as a premier source of precious stones for quite a number of millennia, with roughly 25% of its landmass potentially gem-bearing. The colourful and most durable stones feature a visible, bustling artisanal mining sector as well as high-stakes trading, however, with increasing shares of internationally sourced material. The "invisible" involves deep mysteries, complex geological and gemmological features, and last but not least the emotional attraction of these materials, including the dark sides of wealth and power, some as old as humanity, others with notable changes over time. Insights into human aspects of gemstones are provided, as well as into chemical and physical characteristics of the genesis and the presence of gemstones in a unique spot on earth.