Gem Focus – Feb 2019

Posted on February 5, 2019 by The Gemworld Staff

Amethyst: The Royal Purple

Famous American gemologist G.F. Kunz has written in his book, The Curious Lore of Precious Stones, “while the special and traditional virtue of the amethyst was the cure of drunkenness, many other qualities were attributed to this stone in the fifteenth century.” Indeed, this purple-violet variety of quartz has been revered as the “Bishop’s Stone” for many centuries due to its rarity and attractive color. A multitude of symbolisms and spiritual powers have been ascribed to amethyst throughout millennia and by many different cultures.

Discovery of the vast amethyst sources in Brazil in the 19th century made this stone as common as we see it today. Yet, amethyst is one of the staples of the colored stone trade. Encountered within the realm of most attractive gems, this brightly colored, transparent stone is also one of the most affordable of the classics. Gem grade material occurs in very light to very dark colors. Amethyst is a favorite of expert cutters so precision and fantasy cut material is available. Numerous deposits are known worldwide with Brazil, Uruguay and Namibia being particularly important. Russian material is prized for its rich color. It is not unusual for the finest colored amethyst to appear in the market as “Siberian Amethyst.”

Amethyst, like any other popular gem, is imitated, treated and synthesized. While same colored glass and plastic imitations are easily identified, quench crackled quartz of the same color might fool the hasty gemologist when they skip magnification and only rely on color and refractive index. Most treated amethyst is irradiated which is a method to intensify the color and almost impossible to detect via conventional gem testing methods. Also, it should be noted that the majority of “natural” citrine used in jewelry is actually heated amethyst. However, none of these are an issue compared to non-disclosure of synthetic amethyst in the market. Synthetic hydrothermal quartz is easily and inexpensively produced for many industrial applications. This method also makes varieties of quartz available for the gem market. While the identification is not too challenging, lower priced amethyst and other quartz varieties capacitate overlooking full identification. Since this situation is not disclosed from the very beginning of the production chain, consumers are generally oblivious to high possibility of their jewelry being made out of synthetic amethyst. This is particularly common in inexpensive mass production jewelry set with calibrated stones.

One other feature of amethyst is that it can be found as very large, sometimes gigantic, crystals in nature. This is a remarkably important point for gem carvers because toughness of quartz is well known and preferable for eloquent carvings. However, large crystals over 40 carats would not demand high per carat price as some rarer species such as tourmaline. On the contrary, per carat price starts falling for large cut stones. In the case of carvings, it is the work and the artistry for which the price is paid; size is a secondary concern.

Pricing amethyst for calibrated sizes is generally per piece, while anything larger than one carat would start from $2 and might go up no higher than $55 per carat up to 50ct. in the extra fine category at the wholesale level. Unfortunately, there is no way of practically pricing treated versus untreated material. Buyer must be aware of the synthetic production.

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