HOW THEY FORMED
The formation of these gemstones took place over the course of millions of years within the bedrock in the Crust layer as our planet endured drastic internal changes in pressure due to the flowing, cooling, and solidification of magma. Amethysts formed from a combination of elements, the first one being silica-rich minerals with a touch of ferric iron. Also, a suitable surface, radiation, and the right temperature were intimately involved. As pressure pushed these chemicals upwards they came across oxygen which turned the mix into silicon dioxide, this is the chemical base for quartz which hosts the purple amethysts.
In boiling magma, and within igneous rocks called basalt, pockets of gas formed. These blisters later solidified creating hollow bubbles which explored upwards. These sacs became igneous geodes, formed as the flowing magma transformed into flowing lava. Bedrock rich in different minerals was paramount, as well as the presence of cooling mineral-rich water to seep through tiny cavities in the walls of the geode resulting in the formation of crystals from the wall of the geode inwards towards the hollow center. The geode's round shape shows in some of the amethyst formations.
Sedimentary geodes, scientists believe, formed and hardened around a host such as a tree trunk, or a shell of any kind. As the carbonaceous, organic materials decayed away, the cavity was filled with silica-rich fluids giving birth to the amethyst crystals.
When all these components combined in harmony in very scarce areas of the planet some geodes evolved into these astonishing formations of fossilized minerals, brilliant crystals called amethysts. These remarkable occurrences all took place in the farthest depths of our Earth during the Cretaceous Inferior Period.