Never more popular, the Alexandrite halo rings feature a beautiful gemstone surrounded by sparkling diamonds. A pair of created alexandrite earrings is like two gifts in one. Blue-green by day, and purple-red by night, the color change of this gem is sure to please. White topaz is a popular substitute for the birthstone of April, which is diamond. A pair of white topaz earrings is an affordable alternative to expensive diamond studs.