Hyalite

SiO2·nH2O

Where it forms, where it's found

Geological setting

Volcanic vugs, pegmatite pockets, fumaroles.

128recorded occurrences
Source · OpenStreetMap

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
Transparent · Translucent
Colour
Colorless · white · creme-colored · yellow · orange

no opalescence (play of color)

Streak
white
Tenacity
brittle
Cleavage
None Observed
Fracture
Conchoidal
Density
2.0 g/cm³

Optical

UV response
May show strong green UV fluorescence

Literature, links & citation

Citations
  1. 1973Flörke, O.W., Jones, J.B., Segnit, E.R. (1973) The genesis of hyalite. Neues Jahrbuch der Mineralogie, Monatshefte, H.2, 82-89.
  2. 1994Graetsch, H. (1994) Structural characteristics of opaline and microcrystalline silica minerals. in: Heaney, P.J., Gibbs, G.V., editors. Reviews in Mineralogy Volume 29 Silica - Physical behaviour, geochemistry and materials applications. Mineralogical Society of America, 209-232.
  3. 2016Othmane, Guillaume, Allard, Thierry, Vercouter, Thomas, Morin, Guillaume, Fayek, Mostafa, Calas, Georges (2016) Luminescence of uranium-bearing opals: Origin and use as a pH record. Chemical Geology, 423. 1-6 doi:10.1016/j.chemgeo.2015.12.010DOI: 10.1016/j.chemgeo.2015.12.010
  4. 2017Schindler, Michael, Fayek, Mostafa, Courchesne, Britanney, Kyser, Kurt, Hawthorne, Frank C. (2017) Uranium-bearing opals: Products of U-mobilization, diffusion, and transformation processes. American Mineralogist, 102 (6) 1154-1164 doi:10.2138/am-2017-5700DOI: 10.2138/am-2017-5700
Cite this entry
@misc{mineral2026,
  author    = {Mineral Index editorial board},
  title     = {Hyalite — Mineral Index},
  year      = {2026},
  url       = {https://mineralindex.org/minerals/hyalite-32188},
  note      = {Accessed 2026-05-11}
}