Coral
(kor'- ol')
17th c.; lat. corallum, gr. korallion, sem. goral
Very hard calcareous skeleton secreted by polyp colonies, animals from warm seas, used in jewelry
Color
Light to dark tones of red to orange red
Family
Corallium Rubrum , Nobile or Japonicum
Chemical composition
Mainly CaCO3
Crystal system
Aggregate of calcium carbonate
Hardness (Mohs scale)
3,5 - 4
Specific gravity
2,65 ±0,05
Refractive index
1,486 - 1,658
Optical character
None (aggregate)