ametrine

Ametrine is a transparent to translucent variety of quartz (SiO2) that combines amethyst and citrine colors within a single crystal, typically appearing as purple zones adjacent to yellow or golden zones. The color pattern results from iron impurities and the crystal's exposure to variable heat and irradiation during growth, producing two color states in one specimen.

Natural ametrine forms in hydrothermal veins and geodes where conditions change during crystallization, allowing distinct color zones to develop in the same crystal. Bolivia is the principal source for gem-quality ametrine, with the Anahi deposit noted for its well-defined color zoning; smaller occurrences have been reported elsewhere.

In terms of properties, ametrine is a member of the quartz family, with a Mohs hardness of 7 and a vitreous luster. It is typically transparent to translucent and exhibits a bi-color or multi-zone appearance, with purple amethyst adjacent to yellow to orange citrine. The stone is usually cut to highlight the boundary between the two colors, though some stones show blended zoning.

Care notes are similar to other quartz stones: standard cleaning methods are appropriate, and the stone should be protected from hard impacts or extreme heat that could alter color. Market recognition emphasizes the natural, two-toned color pattern as its defining characteristic.