CS Book 3_AS- 12 Ruby.pdf

Colored Stones 12 KEY CONCEPTS Ruby, especially when untreated, can command the highest Beryllium lattice diffusion is difficult to detect and often per-carat price of all colored stones. requires laboratory analysis. Ruby rates 9 on the Mohs hardness scale, so...

Colored Stones 12 KEY CONCEPTS Ruby, especially when untreated, can command the highest Beryllium lattice diffusion is difficult to detect and often per-carat price of all colored stones. requires laboratory analysis. Ruby rates 9 on the Mohs hardness scale, so it’s ideal for Clarity enhancement is not stable, and a treated ruby’s frequently worn jewelry. appearance might change over time. The most valuable ruby colors are red to slightly purplish red In some lead-glass treated rubies, the proportion of filler is so with medium to medium-dark tone and vivid saturation. high that gem labs consider them composites or manufactured products. The trace element chromium causes rubies to be red, and can also cause fluorescence, which intensifies bodycolor. Thailand is the world’s largest ruby cutting, treatment, and trading center. The finest rubies typically form in marble deposits. Africa has replaced Southeast Asia as the source of the Not everyone agrees on the division between ruby and pink majority of the world’s ruby. sapphire. The Montepuez area of Mozambique has emerged as the The higher levels of iron in basalt-hosted rubies inhibit world’s most important ruby source. fluorescence. Mogok, Myanmar, is the most historically important ruby Never describe a stone by a source name unless you’re sure source. the stone came from that source. Mines in Mong Hsu, Myanmar, supplied most of the world’s commercial-quality rubies through the 1990s. Rubies are almost always heat-treated to improve color and clarity. Along with Thailand, the world’s major ruby cutting and trading centers include China, Sri Lanka, and India. Low-temperature heat treatment can sometimes improve ruby color by removing blue or brown secondary colors, but it is Natural ruby’s rarity encouraged a wide variety of imitations difficult to detect. and inspired experiments in ruby synthesis. High-temperature heat treatment can improve ruby clarity as Introduction of the first synthetic rubies destabilized the well as color. natural gem market until detection methods were established. The high temperatures used during lattice diffusion can result Flux and hydrothermal synthetic rubies have inclusions and in recrystallized areas over parts of a stone’s surface. growth structures that might closely resemble natural rubies. 64