Ametrine

Ametrine is a naturally occurring bicolor variety of quartz that displays both the purple of amethyst and the golden-yellow of citrine within a single crystal. The two colors arise from differing iron oxidation states in adjacent growth zones of the same quartz crystal.

With the same hardness (7) and durability as other quartz, ametrine is a fine jewelry and lapidary material. Lapidaries often cut it to showcase the contrast between the violet and golden zones.

Virtually all natural ametrine comes from a single major source, making it a distinctive and collectible gem.

Ametrine forms when a single amethyst crystal experiences differing temperatures or oxidation conditions across its volume, so that part of the iron-bearing quartz develops amethyst's purple while another part takes on citrine's golden tone. The result is sharply zoned bicolor quartz.

The overwhelming majority of natural ametrine comes from the Anahí Mine in eastern Bolivia, near the Brazilian border, which is the world's principal commercial deposit. Minor occurrences are reported elsewhere, and some bicolor quartz is produced by treating amethyst, but natural Bolivian ametrine dominates the market.

Ametrine is identified by its sharply divided purple and yellow color zones within one transparent quartz crystal, a vitreous luster, hardness of 7, and a white streak. It is doubly refractive with conchoidal fracture and no cleavage.

Natural color boundaries are typically clean and geometric, following crystal growth zones. Look-alikes include heat-treated or assembled bicolor stones and dyed quartz; very even or unnatural color splits can signal treatment. Genuine ametrine shows the same physical properties as amethyst and citrine, since all three are simply colored quartz.

Ametrine is used almost entirely as a faceted gemstone and lapidary material, prized for the striking contrast of purple and gold in a single stone. Custom and fantasy cuts are popular for emphasizing the color zoning.

It is durable enough for everyday jewelry, including rings, pendants, and earrings, and offers good value as an affordable colored gem. Collectors value clean Bolivian material with a crisp color boundary. Metaphysically, ametrine is said to combine the qualities of amethyst and citrine, associated with balance, creativity, and clarity. As quartz, it requires no special care beyond avoiding hard knocks.