Prasiolite and green amethyst are names used to refer to the same green variety of quartz. While they may sound like two different gemstones, prasiolite and green amethyst are actually just different terms used to describe the exact same material.
The name "prasiolite" comes from Greek "prason" meaning leek and "lithos" meaning stone. It was coined to refer specifically to the green quartz formed through heat treatment. Meanwhile, the term "green amethyst" refers more generally to any green-colored amethyst quartz, whether naturally colored or heated to induce the color change.
While prasiolite necessarily refers to heat-treated material, green amethyst can refer to both naturally green quartz as well as heat-treated purple amethyst. Naturally green amethyst is very rare, occurring when trace amounts of iron impurities cause a green coloration instead of the usual purple. So in most cases, green amethyst is simply another term used to describe prasiolite.
The only difference between the two terms is whether the material was originally mined as amethyst and then heat-treated, or whether it formed with a natural green color. But prasiolite and green amethyst from the same origin will be completely identical in their physical properties and appearance. They have the same crystal structure, hardness, specific gravity, refractive index and green color when viewed by the naked eye.
While prasiolite is the more precise and official term recognized by geologists and gemologists, green amethyst is still commonly used in the gemstone industry and jewelry trade. Many jewelers will label heat-treated green quartz as simply "green amethyst" since this name is more familiar to consumers. But scientifically speaking, prasiolite and green amethyst are synonymous.
So in summary, while prasiolite and green amethyst may sound like separate gem varieties, they are in fact the same quartz material. Prasiolite refers specifically to heat-treated purple amethyst that has turned green. Green amethyst can refer to the same heated material, or in rare cases, natural green quartz. Regardless of the terminology used, prasiolite and green amethyst are identical in their physical and optical properties when sourced from the same original quartz material. The two terms can be used interchangeably to describe the beautiful green member of the quartz family.
