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Glossary of watchmaking

Opale

Opale | オパール | 蛋白石

Cuff watch with opal dial, 1,000 brilliants, 1971, Piaget

An amorphous gemstone that shows the spectral colours called fire on either a white or black background. An orange variety called Fire Opal comes from Mexico and does not always have the fire of the other varieties. Opals have a high water content - they can dry out and crack. Thus they are very delicate. Opals have a hardness of 5.5 to 6.5 and a specific gravity of 1.98-2.50