Black Pearl (Tahitian Type)

Physical Properties

Hardness: 2.5–4.5; Color: Dark grey, peacock green, blue, or black with iridescence; Luster: Pearly (pearly-metallic); Structure: Orthorhombic microcrystals; Specific Gravity: 2.60–2.85.

Formation & Geological History

Formed biogenically within the soft tissue (mantle) of a living shelled mollusk, specifically the Pinctada margaritifera. It is a defense mechanism where layers of nacre are deposited around an irritant.

Uses & Applications

Primary use is in fine jewelry (rings, necklaces, earrings). Highly valued for aesthetic beauty and as a status symbol.

Geological Facts

Black pearls are often called 'Tahitian Pearls,' though they can come from various islands in French Polynesia. They are the only pearls with a naturally occurring dark color.

Field Identification & Locations

Identify by checking for 'overtone' (a secondary color shimmying over the surface) and the 'tooth test' (feels gritty against teeth, unlike smooth plastic fakes). Found in warm tropical lagoons.

Identified on: 4/20/2026

Mode: Standard