orthorhombic Mineraloid
Pearl (Aragonite crystal)
Formula CaCO3 (aragonite) + conchiolin
Crystal Structure
#! Species: Pearl (aragonite component)
#! System: Orthorhombic (mmm)
#! Habit: Prismatic aragonite — not pearl morphology
orthorhombic[mmm]:{110}@1.0 + {011}@0.7 + {101}@0.6
orthorhombic
mmm
{110} {011} {101}
Quick Facts
Hardness
2.5
Specific Gravity
2.6
Refractive Index
1.52
Optical Character
Biaxial -
Physical Properties
- Crystal System
- orthorhombic
- Hardness (Mohs)
- 2.5
- Specific Gravity
- 2.6
- Fracture
- Uneven
- Lustre
- Pearly (nacreous)
Optical Properties
- Refractive Index
- 1.52
- Optical Character
- Biaxial -
- Pleochroism
- None
Characteristics
Colours
WhiteCreamPinkGold (South Sea)Black (Tahitian)SilverBlue-greyOvertones (rose, green, orient)
Localities
Persian Gulf (natural, historic)Japan (Akoya cultured)Australia (South Sea)Tahiti (black pearls)China (freshwater)Philippines
Known Treatments
BleachingDyeingIrradiation (for color)Coating
Crystal Forms
prismpinacoid
Notes
Aragonite crystal form — not pearl morphology; pearls are layered nacre aggregates
Related Minerals
Other minerals in the orthorhombic system
