Prasiolite

Prasiolite is a green variety of quartz with a soft leek- to mint-green color. Its name comes from the Greek words for leek and stone. In the trade it is frequently, if inaccurately, sold as "green amethyst."

Most prasiolite on the market is produced by heat-treating amethyst (or certain yellowish quartz) from specific deposits; natural prasiolite is genuinely rare.

The color is gentle and even, prized for clean, eye-clean faceted gems. Because it is quartz, it is durable and affordable compared with many green gemstones.

Natural prasiolite forms when iron-bearing amethyst is altered by natural heat (such as nearby volcanic activity) within its host rock, shifting the color from purple to green. This natural process is uncommon, which is why most material is lab-treated.

Commercially, miners heat amethyst from particular localities, chiefly the Montezuma deposit in Minas Gerais, Brazil, to about 500 degrees Celsius to produce the green color. Some amethyst instead turns yellow (citrine), so only certain deposits yield prasiolite.

Natural occurrences are reported in Brazil, Poland (Lower Silesia), and Canada.

Prasiolite is transparent pale green, hardness 7, with a vitreous luster and conchoidal fracture; it scratches glass. The streak is white.

It is usually clean and faceted; natural-color stones often show weaker, more subtle hues than other green gems.

Look-alikes: Peridot is more yellow-green, doubly refractive to a stronger degree, and softer (6.5-7); green fluorite is much softer (4) with cleavage; green tourmaline and emerald are pricier and have different optical properties. Quartz's hardness and single-crystal habit help separate prasiolite from softer green stones.

Prasiolite is used almost entirely as a faceted gemstone in rings, pendants, and earrings, offering an affordable, durable green stone. Its clarity and quartz hardness make it practical for everyday jewelry.

It has no industrial use beyond ornamental.

Metaphysically it is marketed as a heart-centered "stone of the heart and mind" linking love and intellect, a spiritual association rather than a scientific property. Buyers should know that most prasiolite is heat-treated amethyst, which is standard and stable.