Peridot

Peridot comes in one colour. Not one range with variations at the edges, one colour: green, always, in every stone ever found. It is one of the few gems whose colour comes from an essential part of its own chemistry rather than from a trace impurity, so a colourless or blue peridot is not rare, it is impossible.

What varies is the shade, from a yellowish olive through to a rich grass green, and how much brown is mixed into it. That narrow range is the whole of the quality argument, which makes peridot one of the more straightforward coloured stones to buy and one of the harder ones to sell badly.

This page covers where the colour comes from, the doubling you can see with your own eye, the sources including the two genuinely strange ones, what it costs, and the care it needs, which is more than its hardness suggests.

Why it is always green

Peridot is gem-quality olivine, a magnesium iron silicate. Iron is part of the basic formula rather than a contaminant, and iron in this structure absorbs light in a way that leaves green. Gemmologists call a stone coloured by its own essential chemistry idiochromatic, and peridot is the textbook example.

The proportion of iron to magnesium sets the shade. Less iron gives a lighter, more yellowish green; more gives a deeper and browner one. The most valued material sits at roughly twelve to fifteen percent iron, which produces a pure grass green with no brown and no yellow cast, and that band is narrow enough that fine colour is genuinely uncommon.

There is no treatment that improves peridot's colour, and none in commercial use. Occasionally a fractured stone is filled with resin, which should be disclosed, but heat and irradiation do nothing useful here. What you see is what the ground produced.

The doubling, and what it tells you

Peridot has unusually strong double refraction: it splits light entering it into two rays travelling at different speeds. Look through the table of a peridot of a carat or more with a loupe, or often with the naked eye, and you will see the back facet edges doubled, as though printed slightly out of register.

This is diagnostic and useful. Glass does not do it, and neither does cubic zirconia or synthetic spinel, which are the usual imitations. If you can see clean facet doubling, you are looking at a doubly refractive stone, and in a green stone at peridot prices that is a strong indication it is what it claims to be.

It also has a practical consequence for cutting. Because doubling softens the apparent crispness of the facet pattern, peridot benefits from a well-proportioned cut more than most stones, and a shallow one looks noticeably mushy.

Judging a peridot

Lily pad inclusions are flat discs surrounding a tiny crystal, and they are characteristic of peridot. A few are unremarkable and confirm the stone is natural; a lot of them dull the transparency and should be reflected in the price.

Where it comes from

Myanmar produces the finest material, from the Mogok region, and large clean Burmese stones in pure green set the standard. Pakistan has supplied excellent large crystals since the 1990s from very high altitude deposits in the Kohistan region, sometimes sold as Kashmir peridot. China and Vietnam supply much of the commercial volume.

The United States is a significant source through the San Carlos Apache reservation in Arizona, which produces enormous quantities of small stones and is where a great deal of inexpensive peridot originates. Historically the most famous source was Zabargad, a barren island in the Egyptian Red Sea worked for over three thousand years and the likely origin of most ancient peridot.

The strange ones

Peridot is one of very few gemstones found in meteorites. Pallasite meteorites are stony-iron bodies containing olivine crystals set in a nickel-iron matrix, and a small number have yielded material clean enough to cut. Extraterrestrial peridot is a genuine thing, it is expensive, and it is also a claim that is made far more often than it is true.

It has also been found in lava on Hawaii, where beaches carry green olivine sand, though almost none of that material is of cutting quality. Both facts are true and both are used in sales copy more enthusiastically than the underlying supply justifies.

Hardness and everyday wear

Peridot is 6.5 to 7 on the Mohs scale, which is workable, but its practical durability is worse than that number suggests. It is comparatively brittle, it has a difficult cleavage direction, and it is sensitive to both sudden temperature change and to acids, including the mild ones in perspiration and household cleaners.

It should never go into an ultrasonic or steam cleaner, where thermal shock and vibration can fracture it, and it should be kept away from anything acidic. For rings this argues for a protective mounting; our guide to settings covers the options, and a bezel or a halo that shields the girdle is the sensible instinct for a stone worn daily.

What it costs

Colour first, then size, with the two linked because saturation improves with volume. In dollars per carat:

Peridot is one of the better value propositions in coloured stone. Large clean stones in decent colour remain affordable in a way that emerald, tsavorite and tanzanite of comparable size are not, which is why it turns up so often in substantial cocktail rings.

Meaning and symbolism

Peridot is the August birthstone, sharing the month with spinel and sardonyx, and the August page covers the three. Traditionally it is a stone of light: the Egyptians called it the gem of the sun and mined it at Zabargad under conditions that suggest they took it seriously.

It has been confused with emerald for most of recorded history. Cleopatra's celebrated emeralds were in all likelihood peridot from Zabargad, and the two hundred carat green stones in the Shrine of the Three Kings at Cologne Cathedral, long described as emeralds, are peridot. Few gems have spent so long being admired under another name.

If you are choosing by tradition rather than by month, our astrology and gemstones guide sets out the zodiac schemes, which assign stones on a different basis again.

Designing around a peridot

• Protect the girdle. Brittleness rather than softness is the risk here, and an exposed edge is where it shows. Our settings guide covers the options.
• Buy size. Unusually, colour improves with volume in this stone and prices stay reasonable, so a larger peridot is often the better object as well as the more striking one.
• Yellow gold amplifies the warmth, white metal pushes it towards a cooler green. Yellow gold is the traditional pairing and suits the slightly golden green well. Our metals guide covers it.
• Tell the jeweller what it is. Standard workshop cleaning will damage peridot, and that conversation needs to happen before the ring is handed over, not after.
• Avoid pave next to it. Setting small stones close by means more work near a brittle centre stone, and it invites repairs later.

A short buying checklist

• Look for facet doubling through the table, which distinguishes peridot from glass and from cubic zirconia.
• Judge the green for brown and yellow, which is the whole quality question in this stone.
• Tilt for a window, which shows where weight was kept at the expense of the cut.
• Ask about fracture filling, which is the only treatment that appears here, and should be disclosed.
• Treat meteorite provenance claims with scepticism unless there is documentation.
• For anything substantial, ask for a report from an independent laboratory naming the species.

Frequently asked questions

Why is peridot only ever green? Because the iron that colours it is part of its basic chemical formula rather than an impurity. A peridot without iron would not be peridot. Any other colour is a different stone.

Is peridot treated? Essentially never for colour, since no treatment improves it. Fractured stones are occasionally resin filled, which should be disclosed, but the colour you see is natural.

Is it the same as olivine? Peridot is the gem-quality variety of the mineral olivine. All peridot is olivine; most olivine is not gem quality.

Why do the back facets look doubled? Strong double refraction, which splits light into two rays inside the stone. It is normal, it is diagnostic of genuine peridot, and it is often visible without a loupe.

Is peridot hard enough for an engagement ring? It is borderline. At 6.5 to 7 it resists scratching reasonably, but it is brittle and sensitive to heat and acid. In a protective setting it works; as an exposed daily solitaire it is a risk.

Is peridot really found in meteorites? Yes, in pallasites, and cut material exists. It is also a claim made far more often than it is true, so ask for documentation before paying a premium.

Were Cleopatra's emeralds peridot? Very probably. Egypt had no emerald source of note but did work the peridot island of Zabargad, and the two stones were not distinguished in antiquity.

How do I clean it? Warm water, mild soap and a soft brush, then dry it. Never an ultrasonic, never steam, and keep it away from acids and household cleaners.

To see how it sits against the rest of the coloured stones, the semi-precious stones guide compares the series side by side, and we are happy to answer questions directly (opens in new tab).