三原山温泉 5号井
Miharayama Onsen Well No. 5Operated by · 東汽観光株式会社
Sampled at wellhead
湯
Simple
Classification
Calcium-Sodium Bicarbonate spring
A simple thermal spring drawn from Miharayama Onsen's No. 5 well at a remarkable 84 °C — one of the hotter natural sources on Izu Oshima, cooled before bathing. Neutral pH, hypotonic, and lightly mineralized (0.85 g/kg dissolved solids), so the water reads as quietly gentle on the skin rather than mineral-heavy. What sets it apart is a generous 333.8 mg/kg of metasilicic acid: enough to leave the thin silica film that gives the classic Japanese "beauty-water" feel, smoothing the skin after a soak. Colourless and clear at the wellhead, with no odour and a faint bitter note on the tongue.
pH
6.90
Neutral
Source temperature
84.2°C
Hot
Tonicity
0.85g/kg
Hypotonic
Flow rate
120L/min
Typical
Free CO₂
57mg/kg
Low
- Color
- colorless and clear
- Taste
- slightly bitter
- Odor
- odorless
Highlights
- High silica
- Top-decile hot
Analyzed Nov 9, 2018·株式会社東京水質研究所·Cert no. C9310003
