Colored Stones Key Concepts PDF

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

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