Precious Opal

SiO2·nH2O
Also known as
  • Rainbow Opal
Variety of
Opal
OpalSiO2 · nH2O

Where it forms, where it's found

104recorded occurrences
Source · OpenStreetMap

Varieties

Physical

Hardness
123456789105.5 – 6.5/ 10 MOHS
  1. 1Talc
  2. 2Gypsum
  3. 3Calcite
  4. 4Fluorite
  5. 5Apatite
  6. 6Orthoclase
  7. 7Quartz
  8. 8Topaz
  9. 9Corundum
  10. 10Diamond
Transparency
Translucent
Colour
Multi-coloured
Streak
white
Fracture
Conchoidal

Synonyms

  • Rainbow Opal

Literature, links & citation

Citations
  1. 1964JONES, J. B., SANDERS, J. V., SEGNIT, E. R. (1964) Structure of Opal. Nature, 204 (4962). 990-991 doi:10.1038/204990a0DOI: 10.1038/204990a0
  2. 1964SANDERS, J. V. (1964) Colour of Precious Opal. Nature, 204 (4964). 1151-1153 doi:10.1038/2041151a0DOI: 10.1038/2041151a0
  3. 1966DARRAGH, P. J., GASKIN, A. J., TERRELL, B. C., SANDERS, J. V. (1966) Origin of Precious Opal. Nature, 209 (5018). 13-16 doi:10.1038/209013a0DOI: 10.1038/209013a0
  4. 1971Jones, J. B., Segnit, E. R. (1971) The nature of opal I. nomenclature and constituent phases. Journal of the Geological Society of Australia, 18 (1) 57-68 doi:10.1080/00167617108728743DOI: 10.1080/00167617108728743
  5. 1975Sanders, J. V. (1975). Microstructure and crystallinity of gem opals. American Mineralogist, 60, 749-757.
Cite this entry
@misc{mineral2026,
  author    = {Mineral Index editorial board},
  title     = {Precious Opal — Mineral Index},
  year      = {2026},
  url       = {https://mineralindex.org/minerals/precious-opal-6666},
  note      = {Accessed 2026-05-11}
}