gems, pearl, coral, Arabic mineralogy

Ruska surveys the treatment of pearls and coral in medieval Arabic scientific literature, drawing attention to the mixture of empirical observation, inherited classical ideas and traditional lore preserved in Arabic mineralogical and natural-history texts. For pearls he discusses contemporary explanations of their formation within the oyster, their supposed dependence on environmental conditions, and criteria of quality such as size, brightness, regularity of form and freedom from blemishes. Arabic authors also recorded important pearl-producing regions, particularly the Persian Gulf and Indian Ocean, and described medicinal uses of powdered pearl. Coral is treated in a similar historical manner, with attention to its nature, origin and place within Arabic classifications of mineral, vegetable and animal substances. The article is an early contribution to Ruska’s broader study of Arabic mineralogy and demonstrates the importance of Arabic sources for tracing the transmission and development of premodern knowledge concerning gems and organic gem materials.