Potomac Crystal Rivolis - Birthstone Collection. These high-quality rivolis feature a pointed foiled back to enhance reflection and add dazzling sparkle to your projects. These crystals have no holes and can be incorporated into a variety of bead weaving and wire working techniques to include them in your designs. Be inspired and get creative with this collection of stunning birthstone colors. The Potomac Crystal Rivoli can be used in designs calling for Swarovski 1122. They measure 14mm and come in a pack of 14 (2 of each color).