Definition

Enhancement, when used in gemological conversation, stands for a man-induced treatment which improves the appearance or durability of a gemstone.

Introduction

Gem minerals are rare, durable and beautiful by definition; this is what distinguishes them from all other minerals. Most gem deposits do not solely yield gem grade stones though. In fact, every gem miner will be able to tell you that only a small percentage of the stones he unearths is fit for jewelry. There may be too much or too little color in the stone, the color may be of an undesirable hue or it may be fractured or unstable. Since the demand for gemstones always outweighs the supply, causing their high prices, this is where these non gem grade stones become economically interesting. If a miner can offload his lower grade stones as well as his prime stones his business has got a much better chance on surviving.

Because the natural, untreated product is extremely rare, high prices are commanded throughout the line of production from mine to consumer. Non gem grade stones that are fit for treatment are in greater supply and don't enjoy this natural rarity to the same extend. They can be bought cheap from miners keen to cash their low quality stones so consequently should command lower prices. Relatively inexpensive treatments are then performed to make the stones look exactly like the popular natural product. All too often it takes an expert to distinguish between the natural and treated stones. Now here's where problems may arise. This resemblance makes it possible for unscrupulous dealers to sell the treated product as natural and command top dollar. The proper way to deal with these stones is to disclose the treatments properly.

The price difference between natural and treated goods isn't solely a rarity factor. In some cases the enhanced stones resemble the natural product in appearance but not in durability. A glass-filled ruby for instance isn't as resistant to abrasion and chemical attack as the real deal. This is another reason proper disclosure is of the utmost importance, things that wouldn't affect a natural stone may ruin a treated one.

So, are treatments an evil thing? The answer is no, not when they are properly represented as being treated in one or the other way. The increased prosperity that occurred over the last century allows far more people to indulge in wearing gemstones. Where gems were reserved for the nobility and wealthy in the past, now billions of people have surplus income and are happy to show that off by wearing expensive personal decoration. The demand for gemstones is so big these days that without gem treatments the prices for natural goods would go through the roof.

Treated goods have become an essential part of the jewelry trade. Consumers need them in order to meet their increased demand and the miner needs them to make a consistant living. Without the selling of treatable stones he would be left at the mercy of his luck of finding a gem grade stone every day. It is estimated that 80% of the worlds gemstones are mined by independent artisanal minersand it is important that this group can make a decent living. Without these hard working souls these beautiful gifts of nature wouldn't reach you.

And for the jewelry historian? To those investigating the age of a jewelry item treatments may provide very helpful clues. We have a reasonable good idea of the invention dates of the different treatments and finding a stone which is clearly treated in a way that was invented in the 1970's in a Victorian jewel should raise alarm bells. The stone may either be a replacement of an old stone or indicate a recent reproduction. Either way a closer look is at place in such cases and spotting a modern treatment may contribute to the correct identification of a well made reproduction as such.

Treatments

Below you will find all possible treatments, the gemstones which can be enhanced by these treatments together with the effect of the treatment and the supposed introduction dates of these techniques. Follow the links below to learn more about specific treatments.

Material	Effect	Date of introduction
Heat Treatment
Amber	Small fractures; sun spangles Clarity enhancement Aged look; darkening of surface	BC Wieslaw Giertowski
Beryl	Eliminating the yellow color component in aquamarine	?
Corundum	Enhance clarity by dissolving silk into the corundum lattice Enhance/change color. Introducing asterism by exsolving of silk	BC 1960’s: Gueda sapphire to blue (Crowningshield 1966, 1970, Beesley, 1982.) 1949, Burdick and Glenn patent
Diamond	Annealing after irradiation to introduce color	1957 Crowningshield, G&G Winter 1957
Jade	Lightening or darkening of color Introducing aged look	? ?
Quartz	Changing color	BC
Tanzanite	Changing of brown into blue	1967?
Topaz	Changing of color, Annealing after irradiation	1957 stable blue color product of irradiation in combination with annealing. Pough, 1957
Tourmaline	Changing color	?
Zircon	Changing color Recrystallization of metamict stones	BC ?
Heat + Additive a.k.a Diffusion
Corundum	Surface diffusion, changing color Bulk diffusion, changing color	late 1970s Crowningshield, 1979 Late 1990’s - 2000 Emmett et al
Feldspar	Pipe diffusion, changing color	2008, (Milisenda, 2008, Emmett, 2009)
Irradiation
Beryl	Changing color	1947 (American Mineralogist, vol. 32, p 31-43 jan-feb 1947. Reported in G&G spring 1947)
Corundum	Changing color	1947 (American Mineralogist, vol. 32, p 31-43 jan-feb 1947. Reported in G&G spring 1947)
Diamond	Changing color	1914, Irradiated diamonds by immersion in radium bromide, (Pough & Schulke as reported in G&G spring 1951) 1938, Cyclotron irradiated diamonds (Hardy G&G summer 1949)
Pearl	Darkening	1967, (R.T. Liddicoat G&G spring 1967)
Quartz	Changing/introducing color	1949 (G&G winter 1949)
Spodumene	Changing color	1947 (American Mineralogist, vol. 32, p 31-43 jan-feb 1947. Reported in G&G spring 1947)
Scapolite	Changing/introducing color	(American Mineralogist, vol. 32, p 31-43 jan-feb 1947. Reported in G&G spring 1947)
Topaz	Changing color	1909 irradiation of pink topaz to orange (Pough & Rogers, 1947) 1957 stable blue color product of irradiation in combination with annealing, (Pough, 1957)
Tourmaline	Changing color	(American Mineralogist, vol. 32, p 31-43 jan-feb 1947. Reported in G&G spring 1947)
Zircon	changing color (structure from crystalline to metamict)	(American Mineralogist, vol. 32, p 31-43 jan-feb 1947. Reported in G&G spring 1947)
Filling
Beryl (Emerald)	Clarity/color enhancement by (colored) oil or epoxy resin	Oil – BC Epoxy resin – 1994 ( Levy, 1994 ICA gazette, april)
Corundum	Clarity/color enhancement Oiling Glass filling Flux healing	BC BC Glass filling of surface reaching cavities in rubies 1984 (http://www.ruby-sapphire.com/foreign-affairs.htm Hughes, 1992] Flux healing of surface reaching cavities in rubies 1992 (http://www.ruby-sapphire.com/foreign-affairs.htm Hughes, 1992)
Diamond	Glass filling	1982, Zvi Yehuda
Jade	color/stability enhancement: Impregnation B-jade C-jade	? ? ?
Opal	Impregnation: stability enhancement	?
Turquoise	Impregnation: color and stability enhancement	?
Coating
All gemstones	Adding a colored layer	BC
All transparent gemstones	Adding a transparent layer with different optical density than the gem to create color by interference effects	Early 1940’s (Gubelin, G&G Winter 1949 p. 243)
Diamond	Improving color grade of a diamond by application of coating techniques resulting from WOII research: Vaccuum sputtering of Fluorides on pavilion or girdle	first lab alert 1952 Law enacted against undisclosed marketing of coated diamonds in 1962 by NY State.
Foiling
All transparent gemstones	Enhancing/introducing color, increasing brilliance	Minoan times (Ball, 1950) Roman times (Pliny 76 AD)
Dyeing
All gem materials	Introducing/enhancing color	BC (Pliny 76 AD)
HPHT
Diamond	Color enhancement	1960'ies
Laser Drilling
Diamond	Clarity enhancement	1970 (Crowningshield G&G fall 1970)