Ametrine
Ametrine is a naturally occurring bicolor variety of quartz that combines the violet tones of amethyst with the golden hues of citrine within a single crystal. The color zoning arises from differing oxidation states of trace iron impurities distributed unevenly across growth sectors of the same silicon dioxide crystal. Most commercial ametrine traces back to a single deposit in Bolivia, though heat-treated material is also common in the gem trade.
Ametrine properties at a glance
| Type | Minerals |
|---|---|
| Chemical formula | SiO2 |
| Mohs hardness | 7 |
| Crystal system | Trigonal |
| Luster | Vitreous |
| Streak | White |
| Cleavage | None |
| Fracture | Conchoidal |
| Specific gravity | 2.65 |
| Transparency | Transparent |
| Common colors | Purple and yellow bicolor zoning |
| Rarity | common |
Geology & background
Ametrine forms in hydrothermal quartz veins and pegmatite pockets where a slow temperature gradient across a growing crystal causes iron-bearing fluid to oxidize differently on opposite faces, producing a sharp boundary between purple and yellow zones. The Anahi mine in eastern Bolivia remains the primary commercial source and has supplied the gem market since the deposit's rediscovery in the 1970s, though local accounts of the mine date back centuries. Small quantities have also been reported from Brazil and parts of Asia, but natural material with strong, well-defined color contrast largely traces back to Bolivia.
Because natural ametrine with a sharp, vivid split is uncommon, much of what circulates in jewelry has been produced by carefully heat-treating zoned amethyst-citrine quartz. Collectors should ask sellers whether a piece is natural or treated, since untreated Bolivian material commands a premium. As a variety of quartz, ametrine inherits that mineral's toughness and resistance to scratching, making it durable in jewelry even though it can still fracture under a hard blow.
How to identify Ametrine
Ametrine is identified by its side-by-side purple and yellow zones within a single transparent crystal, a pattern distinct from mixed amethyst-citrine assemblies glued together. It has vitreous luster, a hardness of 7, no cleavage, and the conchoidal fracture typical of quartz. The streak is white, though rarely tested on a transparent gem. Simulants include synthetic quartz grown with artificial color banding and dyed or irradiated glass, both of which lack quartz's hardness and natural inclusion patterns.
- Compare the specimen's color, luster, crystal habit, grain size, streak, and locality before confirming.
- Use multiple photos when possible, including a fresh surface and a close view of texture.
Where Ametrine is found
Reported from multiple localities worldwide; verify locality against specimen provenance when available.
How much is Ametrine worth?
| Entry-level specimen | $2 |
|---|---|
| Typical collector specimen | $20 |
| Premium specimen | $150+ |
Value depends on size, crystal quality, color, locality, rarity, damage, and provenance.
Common uses
- Collector specimens
- Education
- Field identification
- Industrial or lapidary use when suitable
Interesting facts
- The name ametrine blends amethyst and citrine, describing its two-toned parentage within a single mineral.
- Nearly all natural ametrine sold worldwide traces back to the Anahi mine in Bolivia's Santa Cruz department.
- The color split occurs because iron impurities oxidize to different states depending on the crystal's orientation during growth.
Care & safety
Handle as a collector specimen until hardness, cleavage, and fracture are verified.
Avoid inhaling dust. Do not cut, grind, or polish unknown specimens without eye protection and a proper respirator.
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