color filters - bluecolor filters - blue

Color Filters: Uses and Limitations for Gemology


A set of color filters can be helpful in the field and in the lab. Learn the limitations and uses of color filters for gemology.

3 Minute Read

HomeLearning CenterGemologyGemology ToolsColor Filters: Uses and Limitations for Gemology

Color Filters for Gemstone Identification

Color filters are small pieces of plastic that will only allow part of the visible spectrum of light to pass through them. To use one, just shine a bright, full-spectrum light on a gemstone and look at the gem through the filter. Then, compare the color you see to a reference sheet.

Although what you see through a color filter should never be used as proof of a gemstone identification, these tools can help you eliminate some possibilities. Plus, they’re extremely portable, which makes them ideal for examining gems at trade shows.

Chelsea Filter

One of the most popular filters is the Chelsea filter. Originally used on emeralds, it can help you distinguish an emerald lookalike. The Chelsea filter allows yellow-green and deep red light through, so emeralds with chromium as a chromophore glow bright red under a Chelsea filter.

However, emeralds with vanadium as the primary chromophore will appear green. In addition, synthetic emeralds will also glow bright red under the Chelsea filter.

Aside from emerald, other chromium-bearing gems will show bright red under a Chelsea filter. Ruby, jadeite, and alexandrite all contain chromium, and other gems like chrome diopside


Addison Rice

A geologist, environmental engineer and Caltech graduate, Addison’s interest in the mesmerizing and beautiful results of earth’s geological processes began in her elementary school’s environmental club. When she isn’t writing about gems and minerals, Addison spends winters studying ancient climates in Iceland and summers hiking the Colorado Rockies.

Latest Articles

More Articles
Classic Engagement Ring StonesPastel purple sapphire</a>, 1.08 cts, 5.8 mm, round cut, Sri Lanka. © <a href=https://www.gemsociety.org/article/color-filters/"https://www.thegemtrader.com/">The Gem Trader</a>. Used with permission." src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" decoding="async" data-nimg="responsive" style="position:absolute;top:0;left:0;bottom:0;right:0;box-sizing:border-box;padding:0;border:none;margin:auto;display:block;width:0;height:0;min-width:100%;max-width:100%;min-height:100%;max-height:100%;object-fit:cover;object-position:50% 50%"/>

Classic Engagement Ring Stones

Emerald, ruby, sapphire, and diamond are the most popular choices for classic engagement ring stones. Learn more about these traditional...
Read More
Broken Bangle — The Blunder-Besmirched History of Jade Nomenclature: Book Review

Broken Bangle — The Blunder-Besmirched History of Jade Nomenclature: Book Review

Is fei cui a better term for "pyroxene jade" than jadeite? Jeffery Bergman reviews Broken Bangle, a new book on...
Read More
Cuprite Value, Price, and Jewelry InformationJoel E. Arem</a>, PhD, FGA. Used with permission." src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" decoding="async" data-nimg="responsive" style="position:absolute;top:0;left:0;bottom:0;right:0;box-sizing:border-box;padding:0;border:none;margin:auto;display:block;width:0;height:0;min-width:100%;max-width:100%;min-height:100%;max-height:100%;object-fit:cover;object-position:50% 50%"/>

Cuprite Value, Price, and Jewelry Information

One of the rarest of all facetable gems, cut cuprites can show magnificent deep red color. However, these beautiful stones...
Read More
Gemstone Radiation TreatmentPhoto courtesy of <a href=https://www.gemsociety.org/article/color-filters/"https://www.liveauctioneers.com/">liveauctioneers.com and <a href=https://www.gemsociety.org/article/color-filters/"https://www.liveauctioneers.com/auctioneer/1081/eros-auctions-inc/">Eros Auctions, Inc</a>." src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" decoding="async" data-nimg="responsive" style="position:absolute;top:0;left:0;bottom:0;right:0;box-sizing:border-box;padding:0;border:none;margin:auto;display:block;width:0;height:0;min-width:100%;max-width:100%;min-height:100%;max-height:100%;object-fit:cover;object-position:50% 50%"/>

Gemstone Radiation Treatment

Gemstone radiation is a common but little understood technique for altering colors. Learn how it works and what gems usually...
Read More

Never Stop Learning

When you join the IGS community, you get trusted diamond & gemstone information when you need it.

Become a Member

Get Gemology Insights

Get started with the International Gem Society’s free guide to gemstone identification. Join our weekly newsletter & get a free copy of the Gem ID Checklist!