Emerald, The Birthstone for May – Meaning, Properties, and Everything you need to know about it The month of May starts, and we all are going crazy about the May birthstone. The question here is, what is the birthstone for May? Your primary birthstone is none other than one of the four precious gemstones to all those born in May. It's emerald. The beautiful and royal green gemstone is what is assigned as the birthstone of May.