George Frederick Kunz has a book first published in 1913, "The Curious Lore Of Precious Stones" that has a wonderful birthstone chart that includes birthstone from other cultures. Please see the page on Gemstones for further explanations on this topic. Since June's birthstone is normally Alexandrite which is no longer a viable option since it's unavailable, we substitute that gemstone with a Moonstone. This Moonstone reference was mentioned on page 319 in this book and was an adopted birthstone from Kansas City in the early days, thus we call it an Old World Birthstone.
We hand pick these White Moonstones from a Brazilian dealer. Each one has its own unique character with a chatoyant ray of alternate rainbow color. If you see this in stock you are in luck as they are not readily availble. We also have a source in Canada as wells. Happy shopping!