From Crystal Growth Technology

Shuji Oishi
Department of Environmental Science and Technology, Faculty of Engineering, Shinshu University, Wakasato, Nagano 380 8553, Japan

17.1 Introduction

Gemstones are usually used for human ornamentation. Diamond (C), ruby (Al 2O 3:Cr), and emerald (Be 3Al 2Si 6O 18:Cr) are well-known gemstones. The gemstones are principally natural minerals that are highly valued for their beauty, durability, and rarity. Portability is also required for the use of gem materials. The majority of gemstones are single crystals of minerals. As an example of natural minerals, spessartine garnet crystals found at Wada-toge Pass, Nagano Prefecture, Japan, are shown in Fig. 17.1. The garnet crystals have a beautiful glassy luster, and are black and opaque. They can be used for ornamental purposes without cutting. Other gemstones are not single crystals. Opal is one of the best-known non-crystalline gemstones. Natural minerals of good quality are getting scarce with the passing of time.


Figure 17.1: Natural garnet crystals found at Wada-toge Pass, Nagano Prefecture, Japan

The high value placed on gemstones for use in jewelry has led to many attempts to synthesize natural gemstones. The duplication of beautiful gemstones in the laboratory has been one of man's aims. Manmade and natural gemstones have the same chemical composition and crystal structure. Ruby crystals were grown by the flux method in 1837 by Gaudin [1]. He grew ruby crystals of up to 0.187 g from molten potassium alum and potassium chromate. Small emerald crystals were grown from lithium molybdate and lithium vanadate...

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