Peridot Value, Price, and Jewelry Information

Comments

Peridots belong to the forsterite-fayalite solid-solution series, which forms part of the olivine group of minerals. The term peridot refers to green, gem-quality olivine. Forsterite is the magnesium (Mg)-dominant end, while fayalite is the iron (Fe)-dominant end. As idiochromatic gems, peridots get their characteristic green color from iron, an essential element of their chemical structure. In peridot, ferrous iron (Fe²⁺) creates green, while ferric iron (Fe³⁺) creates yellow. Traces of chromium (Cr) in peridots don't cause hue but may make the green color brighter.

An iron content of just 12 to 15% in olivines creates the ideal peridot color, whereas higher levels create a “muddier” brown color. Thus, olivines closer in composition to the forsterite end tend to be greener. In contrast, those closer to iron-dominant fayalite tend to be yellower and browner. Therefore, most peridots are closer to the forsterite end.

Cat's eye and star stone peridots are known but very rare. In cabbed gems, inclusions can create a star with a weak cross or a distinct 4-ray effect.

What is Chrysolite?

The modern August birthstone has a long history. The celebrated Isle of St. John (or Zabargad, Egypt) in the Red Sea has produced peridots since the time of Ancient Egypt. This site has also produced one of the most confusing name mixups in gemology. The Ancient Greeks called this island Topazios, which was said to produce a yellow-green gem. This name for the island eventually led to the name topaz for those famously (but not exclusively) yellow gems.

Oddly enough, the gem modern gemology identifies as topaz doesn't occur on this island. However, gems from this island were also called chrysolite, Greek for “golden stone.” By the 19^th century, chrysoberyl, prehnite, and peridot (all green to yellow-green gems) were called chrysolite.

You might still encounter the term chrysolite used synonymously with peridots or sometimes in reference to intermediate members of the olivine forsterite-fayalite series. Nevertheless, gemologists today no longer use this term. Topaz, chrysoberyl, prehnite, and peridot (olivine) are all considered distinct gem species.

Peridotite

Olivines (those from Earth, not from outer space) form in the Earth's mantle. Peridotite, an igneous rock made primarily of olivine and pyroxene, makes up most of the upper mantle.

Fayalite

Brown olivine gems, rich in iron, can be very beautiful, especially when the color runs more golden than brown. Although very rarely found in nature, fayalite commonly occurs in iron slag produced by metallurgical processing.

Identifying Characteristics

Properties of Gem Olivines

Greenish peridots generally have a specific gravity (SG) of 3.3 to 3.4; brownish stones about 3.5.

Birefringence

Peridots have very strong double refraction, which can produce doubling and fuzziness effects. This can help identify them.

Absorption Spectrum

Peridot shows a strong iron spectrum with three main bands:

• Strong at 4930
• Narrow at 4730
• Broad at 4530

While peridot also shows some vague bands at 6530 and 5290, the set of three evenly spaced bands is distinctive.

Inclusions

Under 10X magnification, peridots will often reveal a distinctive, disk-like liquid-and-gas inclusion. Known as “lily pad” inclusions (or sometimes “lotus leaves”), these may form around spinel or biotite crystals as well as cavities.

Synthetics and Simulants

Scientists have synthesized both forsterite and peridot olivines using melt techniques. Dr. Kurt Nassau notes that chromium-doped synthetic forsterites have commercial applications for laser research and have also surfaced in jewelry. This material can be distinguished from natural forsterites and peridots due to lower SG and refractive index (RI) values as well as chromium-related features. However, synthetic peridot, grown for experimental purposes, may only differ from natural gems by its inclusions. (Gems & Gemology, Summer 1994, Vol. 30, No. 2).

While actual synthetic peridots may still have no general commercial availability or economically viable jewelry use, you can find many simulated peridots on the market. In green colors, synthetic corundum and spinel gems, as well as cubic zirconia, may be passed off as peridots.

Some natural green gems can be confused with peridots, such as emeralds and demantoid garnets. Gemologists can distinguish the properties of these gems fairly easily. However, you're more likely to find peridots presented as emeralds and demantoids than vice versa, due to their greater value.

Perhaps the most frequently encountered peridot simulant is green glass. Although visually very similar, their physical and optical properties differ significantly.

Enhancements

Most peridots don't normally receive treatments. However, some cut peridots may be metal-foiled to improve their stability and color, like faceted glass.

The lozenge-shaped peridot in this beautiful early 20th-century pendant has a foil back. Photo courtesy of liveauctioneers.com and Fellows.

Sources

Zabargad (Zebirget), Egypt

This island lies about about 35 miles off the coastal port of Berenica in the Red Sea. The most ancient known source of peridots, this often fog-shrouded location proved difficult for ancient navigators to find. In fact, it had been lost for centuries until rediscovered in 1905. Zabargad produces peridot crystals in veins of nickel ore in an altered peridotite rock. This material has a very rich, not too dark, medium green color.

Myanmar

The world's only major source of very large peridots, the slopes of Kyaukpon, near Mogok, produce the material in masses. This rough yields dark green, oily, transparent gems of fine color, some several hundred carats in size.

Arizona and New Mexico

Here, peridots can occur as grains, fragments of parent rocks now long eroded that ants use to build large hills. Peridot is also mined on the Navajo Reservation. These pieces usually yield small cut stones, under five carats, with occasional larger gems.

Norway

Ameklovdalen, Sondmore produces peridots paler than those from other localities. These gems have a lovely lime-green hue because they contain less iron, but cuttable pieces are very rare in large sizes and seldom yield cut stones over five carats.

Other Notable Sources of Gem Quality Olivines

• United States: Riverside, San Bernardino County, California; Hawaii (in volcanic bomb nodules); Bolton, Massachusetts.
• Mexico: the state of Chihuahua contains one of the world’s largest olivine deposits. Similar to Arizona peridot, the material also occurs in brown grains.
• Ratnapura, Sri Lanka: olive-green gems; also nearly colorless material, the closest in composition to forsterite of any known gem olivine.
• Kenya: brown crystals; Emali produces gem quality material.
• Ross Island, Antarctica: some cuttable material.
• Mt. Batchelor, North Queensland, Australia: yellow-green, dark green, gemmy; potential for stones up to about 20 carats.
• Minas Gerais, Brazil; China; Finland; Germany; Greenland; Italy; New Caledonia; Pakistan; Russia; Umba district, Tanzania; Vietnam.

Peridots can also have extraterrestrial origins. Pallasite meteorites have yielded facetable peridots.

Stone Sizes

Myanmar material cuts the largest gems, followed by Egyptian material. Peridot from Antarctica is limited to a few stones under 2 carats. Arizona material over 10 carats is very rare in cut form.

• Smithsonian Institution (Washington, DC): 310 (Egypt); 287 (Myanmar); 22.9 (Arizona).
• Royal Ontario Museum (Toronto, Ontario, Canada): 108, 87.1, 83.3 (Myanmar).
• Devonian Group (Calgary, Alberta, Canada): 82.4, 24.7 (Myanmar).
• Geological Museum, London: 136 (Myanmar).
• Topkapi Museum, Istanbul: many large and fine cabochons.
• Private Collections: 284.85 (Egypt); 34.65 (Arizona).

An immense (100-ct plus) clean crystal from Norway (by far the largest known) resides in a European collection.

Care

Olivines can range in hardness from 6.5 (fayalite) to 7 (forsterite). Thus, peridots can approach quartz gems in hardness. However, they are still sensitive to scratching from household dust (which has a hardness like quartz). Furthermore, they have some susceptibility to stress fractures.

Use protective settings for any peridot rings. Avoid settings that place stress on peridots and clean them only with a soft brush, mild detergent, and warm water. Peridots also have some sensitivity to acids, even those found in perspiration. Peridot jewelry should be worn against the skin only occasionally.

Consult our gemstone jewelry cleaning guide for more recommendations.

Joel E. Arem, Ph.D., FGA

Dr. Joel E. Arem has more than 60 years of experience in the world of gems and minerals. After obtaining his Ph.D. in Mineralogy from Harvard University, he has published numerous books that are still among the most widely used references and guidebooks on crystals, gems and minerals in the world.

Co-founder and President of numerous organizations, Dr. Arem has enjoyed a lifelong career in mineralogy and gemology. He has been a Smithsonian scientist and Curator, a consultant to many well-known companies and institutions, and a prolific author and speaker. Although his main activities have been as a gem cutter and dealer, his focus has always been education. joelarem.com

View All Articles

Donald Clark, CSM IMG

The late Donald Clark, CSM founded the International Gem Society in 1998. Donald started in the gem and jewelry industry in 1976. He received his formal gemology training from the Gemological Institute of America (GIA) and the American Society of Gemcutters (ASG). The letters “CSM” after his name stood for Certified Supreme Master Gemcutter, a designation of Wykoff’s ASG which has often been referred to as the doctorate of gem cutting. The American Society of Gemcutters only had 54 people reach this level. Along with dozens of articles for leading trade magazines, Donald authored the book “Modern Faceting, the Easy Way.”

View All Articles

Barbara Smigel, PhD. GG

Barbara Smigel is a GIA certified gemologist, facetor, jewelry designer, gem dealer, gemology instructor and creator of the well-regarded educational websites acstones.com and bwsmigel.info.

View All Articles

International Gem Society

View All Articles