Leon likes amethysts because he loves being purple. (And, of course, It has nothing to do with Trudy's love for the same color.) 😉
Amethyst, in its natural state, can be light lavender to pale violet to deep purple colored quartz. It owes it's color to irradiation, impurities of iron &, in some cases, transition metals & other trace elements.
It was used as a gemstone in ancient Egypt. Ancient Greeks believed it could prevent intoxication while medieval European soldiers wore them as amulets for protection in battle believing they could heal people & keep them cool headed. Anglican bishops wear an episcopal ring often set with an amethyst. In ancient China it was used as a powerful tool to remove negative energies & drive away the hazards of daily life.
The earliest reference to amethyst as a symbol of sobriety is found in a poem by Asclepiades of Samos sometime after 320 BCE.