Surface coating of gemstones explained

Published by Gordon Weller GIA GG on 9th Aug 2016

Gemstone Coating aka Surface Coating or Surface Modification

Coating (aka surface coating or surface modification) gemstones is a treatment technique which dates back hundreds of years. Its purpose is to make a gemstone more desirable by creating or changing its color. Originally, the primary means of surface modification involved putting backings behind a stone, such as colored foil, or to strategically apply small amounts of paints or inks to the back of the gemstone, known as painting. The foil, paint, ink or other colored substance would produce a new, more desirable color once the stone was mounted in a piece of jewelry. Patterned foils could create special effects, such as stars, in some stones.

Possibly, you’ve encountered some antique costume jewelry that, when the ‘diamond’ was removed, it was actually glass or a common colorless gemstone, with a metallic foil back. The use of foil was mostly associated with inexpensive jewelry and usually not intended to deceive. The primary purpose of painting a gemstone, however, was to deceive a potential buyer into believing a common material was a more valuable gemstone.

As with most gemstone treatments, coating techniques have become more sophisticated with time. Today, coatings are applied using complex technology. Metals, such as gold, titanium, copper, etc., can be vaporized and introduced in a vacuum environment where a thin layer adheres to an often colorless gemstone, creating amazing colors and effects. Surface modification is not considered permanent. The surface coating can be scratched, damaged or worn away.

In our 100 East and Sas E Gems branded jewelry, we use only gemstones whose treatment is considered permanent under normal circumstances. It is possible that jewelry offered as Gordon's Curated Selection could contain coated gemstones. Carefully review the Product Detail information for any piece of jewelry you're seriously considering. That's where we disclose all treatments our gemstones receive.

A friend recently returned from a Caribbean cruise, which included a number of port stops with many jewelry shops. She told me about a ring she nearly bought with the most unique gemstone she’d ever seen. The salesperson called it Caribbean topaz, a special topaz stone found only in the Caribbean. The large center stone sparkled with a rainbow of iridescent colors, which she found fascinating. I asked what the salesperson told her about the Caribbean topaz and why she didn’t buy the ring. She said the salesperson spoke only about the gemstone’s unique beauty and that it could only be found in the Caribbean. She ultimately didn’t buy the ring because, despite its appeal, it simply cost more than she planned to pay.

I told her the salesperson was actually selling a common, colorless topaz gemstone with a metallic coating which created the iridescence she found so appealing. I further explained the coating is not permanent and could be damaged from normal wear, causing the iridescent effect to disappear.

I assured my friend that coating plain gemstones to make them more appealing is considered an acceptable practice within the jewelry industry. Many people find them unique and affordable alternatives to fine gemstones. What I found objectionable was the salesperson either didn’t know or purposely didn’t inform her the stone was treated to create this beautiful iridescent effect, and that the treatment wasn’t permanent. With full disclosure about the stone’s treatment and durability, she could have properly evaluated the ring’s value proposition.

In the end, my friend was happy she didn’t buy this amazingly unique ring only to be surprised at some point in the future that the stone was treated and the treatment wasn’t permanent.

Speaking of topaz, click on the link if you’re interested in seeing the 100 East Fine Jewelry blue topaz jewelry collection.