CS Book 1_ AS- 6 Treatments PDF

Treatments KEY CONCEPTS Treatments that improve gem appearance and quality increase the supply of commercially important gems. To help build trust in the gem and jewelry industry, all treatments—even suspected or probable treatments—should be disclosed as part of every transaction. Gems that are com...

Treatments KEY CONCEPTS Treatments that improve gem appearance and quality increase the supply of commercially important gems. To help build trust in the gem and jewelry industry, all treatments—even suspected or probable treatments—should be disclosed as part of every transaction. Gems that are commonly heat-treated include corundum, tanzanite, zircon, topaz, aquamarine, and amber. When certain trace elements within a gem lose or gain electrons during heat treatment, it can change the way the gem absorbs light, altering its color. Heat treatment can alter corundum color and create or eliminate phenomena and inclusions. Low-temperature heating can improve the appearance of ruby and pink sapphire by removing blue color zones. Low-temperature heating of corundum is much more challenging to detect than higher-temperature heating. Producing blue color in geuda sapphire requires hightemperature heating in a reducing environment, followed by relatively rapid cooling. Quantities of lattice-diffusion treated corundum, feldspar, and spinel had entered the gem market by 2015. Lattice diffusion with heavier elements like titanium and chromium produces a shallow layer of color that might be removed by minor repolishing. A combination of beryllium diffusion and heat treatment can improve color in some dark blue sapphires and make them more marketable. The color resulting from lattice diffusion with beryllium can penetrate the entire stone. Fracture filling is the most common form of clarity enhancement. Today, almost all emeralds on the market are subjected to clarity enhancement. Filling with glass or resin can stabilize highly fractured, otherwise unusable rough so it can be processed for jewelry use. The proportion of filler in some lead-glass treated gems is so high that gem labs consider them composites or manufactured products. Irradiated color is not always stable, and exposure to heat or light can destroy it. Commonly irradiated gems include topaz, tourmaline, and cultured pearl. Bleaching is a fairly common pearl treatment. Jadeite is often treated with a combination of bleaching and impregnation. Dyeing is one of the oldest gem treatments. Commonly dyed gems include cultured pearl, lapis lazuli, chalcedony, and coral. 301