Dark purple or dark amethyst, is quite different from "sunshine purple" in that this glass is colored from its origin and not by the sun. I have found a couple of pieces on the US west coast, and a couple of pieces in the south of France.
North Beach Treasures: Extremely Rare Sea Glass
De Grisogono Amethyst and Turquoise
amethyst & diamond ring ♥
14K White Gold The Royal Ring
An Art deco amethyst and diamond brooch/pendant Dual use: the brooch with a geometric surmount of faceted amethyst and millegrain-set diamond detail, to a large polished amethyst drop with similarly-set diamond cap; as a pendant with similarly-set diamond surmount loop, converted from a pendant, circa 1925
Art Nouveau. Gold and Amethyst Necklace, Tiffany, c1900.
Division of Mineralogy - New Acquisitions - Amethyst Necklace
Guided by stars, kissed by moonlight, she left a trail of glitter. ~ Amethyst and the Moon
Victorian Carved Amethyst, Diamond And Gold Beetle Brooch (The beetle or scarab was the symbol of fertility and eternity)
Amethyst Purple Lavender Copper Handmade Beaded Net Rope Bracelet | jazzitupwithdesignsbynancy - Jewelry on ArtFire
Year of the Horse in Jewelry ~ An Amethyst, Emerald and Diamond Bangle Bracelet, by David Webb. Photo courtesy of Christie’s