Product Code SKU7008. 9ct Yellow Gold 6mm x 4mm oval Natural Ruby Earrings Ruby is the birthstone for July as well as the 40th anniversary. Rubies are one of the most valuable gemstones. Rubies, like sapphires, are technically corundrum with the red usually being created by the addition of trace amounts of Chrome. Because chrome is both rare, and because it tends to cause rubies to develop fissures, finding larger, higher clarity rubies can be a very difficult proposition. Lab-grown rubies are an alternative to mined rubies giving eye clean stones at an affordable price. Beautifully presented in a gift box.