For the month of May we celebrate two luscious green stones: emerald and chrysoprase.
Emeralds are formed when chromium, vanadium, and iron are present in the mineral beryl. The varying presence of these three elements gives emerald its range of color. Chromium and vanadium make an intense green color. Iron gives the stone a bluish tint. Source: https://www.gia.edu/seeing-green
Chrysoprase, a variety of chalcedony, derives its colour from nickel. Source: https://www.gemsociety.org/article/chrysoprase-gem-information/