Gem Focus – April 2020

Posted on April 13, 2021 by Çiğdem Lüle, PhD, FGA, GIA GG, DGA

Pyrite: Fool’s gold also masquerading as marcasite.

Pyrite, a common iron sulfide that crystalizes in the cubic system, is a very attractive mineral when found in large sizes. Almost sculptural, single or intertwined pyrite crystal stacks are the best specimens to win new collectors. While it may be mined in many countries as the iron ore, collectable specimens from Spain and Peru are quite famous. It is also seen in the fossilization process, so pyritized fossils such as ammonites are popular items too. When pyrite is not the main object, but an inclusion in a gem material, it has pros and cons. As a natural inclusion in many gemstones from emeralds to quartz, it assures the natural origin, therefore, is a welcome feature. However, once it is found in jet or lapis lazuli, for example, it will obstruct the polishing process.

Vintage sterling silver rose design earrings embellished with marcasites.
Courtesy of Lang Antiques.

Gemologists are not strangers to pyrite for several reasons. For one, it is always fun to explain why it is called “fool’s gold” to clients. The other more serious reason is to recognize that commonly called “marcasite” jewelry is in fact set with pyrite. Marcasite is a rarer form of iron sulfide that crystalizes in the orthorhombic system and very much looks like pyrite. It is quite brittle, hence not very suitable for setting. Although it’s been used in jewelry by ancients, marcasite has become fashionable around the 18th century since its metallic luster in silver setting would look very much like diamond jewelry. The tradition still goes on today and it is almost always sold as marcasite jewelry, despite the fact that it is pyrite. One other common use of pyrite today is in bead form. There are many shapes and sizes of pyrite beads in the market. Whether they are left in their cubic form or shaped as “freeform” beads, they provide great natural metallic gem pieces in modern designs.

Diamond, pyrite, gold, sterling silver bracelet, Frederica Rettore.
Courtesy of Heritage Auctions.

Modern jewelry designers explore every natural object as a gemstone and pyrite is not an exception. There are notable jewelry pieces in the market set with rough or cut pyrite as the center gem, some of which are even auctioned due to their provenance. After all, who wouldn’t want to own a pair of pyrite and gold cufflinks once worn by famous astronaut Neil Armstrong?

Value of pyrite is as diverse as its use. While pyrite crystal specimens or pyritized fossils from famous localities would fetch thousands of dollars, small faceted pieces or beads would be sold in bulk for a few dollars only. Naturally, any custom jewelry piece would be valued based on the design and the designer, not the pyrite itself.

Pyrite, perhaps with an unfair name of fool’s gold, seems to be quietly established in our gem and jewelry world for longer than we know. Whether it is a beautiful sparkle in lapis lazuli or tiny pieces set in silver, it will remain even longer.

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