Siderite Value, Price, and Jewelry Information
Siderite is difficult to cut, but this light brown collector's gem has yielded faceted pieces of great beauty.
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Siderite is difficult to cut, but this light brown collector’s gem has yielded faceted pieces of great beauty.
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What is Siderite?
Siderite forms three solid-state solution series. It's the iron (Fe) analogue in a series with manganese (Mn) dominant rhodochrosite. It also forms the Fe-end of a series with zinc (Zn) dominant smithsonite, as well as with magnesium (Mg) dominant magnesite.
Siderite has been used as an iron ore and for steel production. Material from Cornwall, England has been called "chalybite," after the Greek word for steel, referring to its iron and carbon content.
Does Siderite Make a Good Jewelry Stone?
Rhodochrosite, smithsonite, and magnesite have attracted some interest as cabs and rare transparent faceted pieces, despite their low hardness. On the other hand, gem cutters don't typically cab siderites. In addition to low hardness and perfect cleavage, the massive material suitable for cabbing is unattractive. (Evidently, the surge of popular interest in earth-tone gems hasn't yet reached siderites).
You're more likely to find siderites on display in mineral and gem collections than worn as jewelry pieces. They're difficult to cut and too soft for ring use without protective settings. They would be best reserved for occasional wear. Use for earrings, pendants, and brooches would be more advisable.
Nevertheless, as faceted pieces, these golden and honey-colored gems would make unusual, prized additions to show off in any gem collection. In particular, Portuguese rough has yielded beautiful faceted stones.
Are There Synthetic Siderites?
Scientists have synthesized siderite to study its use for the removal of fluoride and arsenic from water. The synthetic material also has applications for agronomy as well as lithium ion batteries. However, this synthetic material has no known jewelry use.
Due to their similar colors and hardness, siderites may be misidentified as rhodochrosites, smithsonites, or magnesites. Nevertheless, gemologists can distinguish them based on differences in specific gravity as well as optical properties.
Siderites usually receive no treatments or enhancements.
Where are Siderites Found?
Panesqueira, Portugal has produced fine, light brown crystals, some transparent. Minas Gerais, Brazil, has also yielded large and fine crystals.
Other notable gem-quality sources include the following:
- Mt. Ste. Hilaire, Quebec, Canada: brown rhombs up to 15 inches on edge.
- Ivigtut, Greenland: rich brown, gemmy-looking crystals in cryolite.
- Cornwall, England: greenish crystals, some transparent (chalybite).
- United States: Colorado; Connecticut; Idaho.
- Austria; France; Germany; Italy.
Rare faceted pieces usually range in size from 1 to 5 carats.
- National Museums of Canada (Ottawa, Ontario): 2.60. 2.25 (light brown, Quebec, Canada).
How to Care for Siderites
Store siderites separately from other stones to avoid contact scratches. Avoid cleaning these gems with mechanical cleaning systems, like steam and ultrasound. Clean them only with a soft brush, mild detergent, and warm water. 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
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