Queensland's Central Highland towns of Anake, Rubyvale, Sapphire and The Willows are home to the largest sapphire fields in the Southern Hemisphere. Like many of the wonders along the Tropic of Capricorn the "Dig the Tropic" drive route, the Sapphire Gemfields are a product of incredible time and drastic changes in climate and environment. Between 40 to 70 million years ago as the earth's crust shifted moving Australia closer to its current position, hot spots developed below. Plugs of the Mount Hoy Basalt erupted spewing out basaltic ash and lavas. Abundant sapphires and zircons that had formed deep in the earth's crust, blasted out as crystals in the volcanic ash. The Sapphire Gemfields are famous for rich, golden yellow and parti-coloured stones and are also home to the famous black star sapphires. Heading west, finish your journey at Alpha where dramatic shifts in Tectonic plates formed the Drummond Range - home to petrified wood.