Pearl
A pearl is a hard, glistening object produced within the soft tissue of a living shelled mollusk or another animal, such as fossil conulariids. Just like the shell of... Wikipedia
- Category: Carbonate mineral, protein
- Formula, (repeating unit): Calcium carbonate, CaCO 3, Conchiolin
- Strunz classification: 05.8
- Crystal system: Orthorhombic
- Color: White, pink, silver, cream, brown, green, blue, black, yellow, orange, red, gold, purple, iridescent
- Cleavage: None
- Fracture: Uneven, various
- Mohs scale hardness: 2.5–4.5
- Streak: White
- Specific gravity: 2.60–2.85
- Refractive index: Common pearl: 1.52-1.66, Black pearl: 1.53-1.69
- Birefringence: 0.156
- Pleochroism: Absent
- Dispersion: None
- Ultraviolet fluorescence: White pearls: light blue to light yellow, Yellow and golden pearls: yellow-green, greenish brown to dark brown, Black pearls: commonly pink to orange-red
- Data source: DuckDuckGo