orthorhombic Carbonates
Aragonite
Formula CaCO3
Crystal Structure
#! Species: Aragonite
#! System: Orthorhombic (mmm)
#! Habit: Prismatic with multiple dome faces
orthorhombic[mmm]:{110}@1.0 + {010}@0.7 + {011}@0.6 + {021}@0.4
orthorhombic
mmm
{110} {010} {011} {021}
Quick Facts
Hardness
3.5
Specific Gravity
2.93
Refractive Index
1.53
Optical Character
Biaxial -
Physical Properties
- Crystal System
- orthorhombic
- Hardness (Mohs)
- 3.5
- Specific Gravity
- 2.93
- Cleavage
- Good {010}, poor {110} and {011}
- Fracture
- Subconchoidal to splintery
- Lustre
- Vitreous to resinous
Optical Properties
- Refractive Index
- 1.53
- Birefringence
- 0.155
- Optical Character
- Biaxial -
- Dispersion
- 0.014
- Pleochroism
- None
Characteristics
Colours
ColorlessWhiteBlueYellowGreenBrownOrange (flos ferri variety)
Localities
Spain (Aragon - type locality)Morocco (spectacular twins)Namibia (blue)MexicoUSA (various)Worldwide in caves and hot springs
Crystal Forms
prismpinacoidpseudohexagonal twins
Notes
Extremely high birefringence; dissolves in dilute HCl with effervescence; forms nacre in shells
Related Minerals
Other minerals in the orthorhombic system
