Siliceous sinter
Chemical Process (Liquid-phase growth) - Ground surface
Required Geological Setting
Occurrence
A kind of hot spring sinters composed of amorphous silicic acid or opal deposited from hot spring water. Silicic acid dissolved in hot spring water deposits as amorphous silicic acid, [SiOx(OH)4-2x]n, by water temperature lowering or pH increasing. Silicic acid can deposit stably in the wide pH range between 1.0-10.0, and pure white silicic acid (siliceous sinter) deposits from acidic hot spring water with a pH less than 1.0. Silicic acid deposits with amorphous iron oxides in the pH range between 3.0-7.0 from iron containing hot spring water, and colored silicic acid such as Tsugaru-Nishiki-ishi is formed. These silicic acid changes to jade or agate during diagenesis. Some locations produce transparent globular aggregates of siliceous sinter.
![Siliceous sinter](sinter.gif)
Distribution of siliceous sinter described in this site. Deposits align along continent-side (Eastern side) of the volcanic front. The yellow line is the volcanic front.
Reported Minerals
- Siliceous sinter
Localities
- Jakotsu River (Siliceous sinter)
- Atami Hot Spring (Siliceous sinter)
Related Occurrences
- Travertine (Calcareous sinter)
- Siliceous sinter
- Sulphur sinter
- Bog iron
- Vitriolic sinter
- Wad