Birthstone for June and Gemini
Moonstone, Alexandrite and Pearl are considered the birthstones for June and Gemini. The pearl is believed to be for Joy, Love and Fertility. One may also find Citrine, White Sapphire and Agate assigned to Gemini.
Having a son called Alexander born under the sign of Gemini, one of my favorites is Alexandrite. It was originally found in the Ural Mountains in Russia in the 1830's hence being named after Tsar Alexander II.