Ametrine

Ametrine is a kind of quartz, the silicon dioxide mineral, in which purple and yellow-to-orange zones sit side by side within one crystal; its name joins the words amethyst and citrine. Wikipedia explains that both colours come from traces of iron held in different oxidation states, the yellow parts having been oxidised by heat, and notes that some authorities will not call the yellow part true citrine. Natural ametrine comes almost entirely from one Bolivian mine, with further deposits in Brazil and India, though much of what is sold was made by heating or irradiating amethyst, and cheap stones may be synthetic. It is also called trystine, golden amethyst and, in the trade, bolivianite. Hall describes it as a transparent crystal, usually small and tumbled, and treats it as joining the qualities of amethyst and citrine. She associates it with protection during astral travel, calmer and more focused meditation, opening the third eye for healing and divination, clear thinking, creativity and emotional transformation, and says its cleansing action clears negativity from the aura. She suggests wearing it against the body for long stretches.