From Longman Dictionary of Contemporary Englishamethystam‧e‧thyst /ˈæmɪθɪst/ noun 1 
DCJ[countable] a valuable purple stone used in jewellery2 CC[uncountable] a light purple colour —amethyst adjective
DCJ[countable] a valuable purple stone used in jewellery2 CC[uncountable] a light purple colour —amethyst adjectiveExamples from the Corpus
amethyst• On display are earrings, necklaces and bracelets made from lapis, carnelian turquoise, jade, amber and amethyst.• Behind him on a finely carved desk was a gleaming working model of the St Petersburg-Cannes Express constructed in pearls and amethysts.• The glass is only one millimetre thick, and is pale amethyst in colour.• The Romans believed the amethyst prevented drunkenness and used to drink out of goblets studded with these purple gems.• There were the unfinished shoes for Emily Grenfell lying on the bench, the amethysts agleam against the softness of the leather.• Overhead, in the amethyst dusk above the Viennese Altstadt, Steel City was an evening star.• We drove through undulating farmland and it was as if the light were refracted through amethyst.• Two fifteenth-century icons set in beaten silver, studded with amethyst and quartz.Origin amethyst (1200-1300) Old French amatiste, from Latin amethystus, from Greek, “preventer of drunkenness, amethyst”, from methy “wine” 