Organic Gemstone
Black Pearl (Tahitian Type)
Aragonite / Pinctada margaritifera (CaCO3 + Conchiolin)
Hardness: 2.5-4.5 (Mohs scale), Color: iridescent black, grey, or peacock green/purple; Luster: Pearly (orient/overtone); Structure: Microcrystalline layers; Specific Gravity: 2.60-2.85
- Hardness
- 2
- Color
- iridescent black, grey, or peacock green/purple
- Luster
- Pearly (orient/overtone)
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Physical properties
Hardness: 2.5-4.5 (Mohs scale), Color: iridescent black, grey, or peacock green/purple; Luster: Pearly (orient/overtone); Structure: Microcrystalline layers; Specific Gravity: 2.60-2.85
Formation & geological history
Formed biologically within the soft tissue of a living shelled mollusk. Layers of nacre are secreted around a microscopic irritant. Most modern specimens are cultured in lagoons around French Polynesia.
Uses & applications
Primarily used in high-end jewelry (necklaces, rings, earrings) and for luxury collectors. Historically used in cultural ornamentation.
Geological facts
Black pearls were once considered the rarest gems on earth. Unlike white pearls, which are often bleached, Tahitian pearls are naturally dark due to the black-lipped oyster's shell edge.
Field identification & locations
Identify by 'tooth test' (gritty against teeth, unlike smooth plastic imitations), irregular organic shape (baroque), and deep rainbow iridescence. Found in warm tropical Pacific waters.
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