Iron Ion (Gantesen) Analysis | Heat Retention & Anemia Benefits

Table of Contents

What is Iron ion?
Main Effects
Iron ion Top 5 Hot Springs

What is Iron ion?

Iron(II) ion (Fe²⁺) is the marker of iron-rich springs. The water turns yellow-brown to red-brown when exposed to air, offering strong heat retention.

Main Effects

Strong heat retentionThe iron content in the water forms a thin film on the skin. This coating helps to prevent body heat from escaping after you get out of the bath, keeping you warmer for longer.
Indicated for iron-deficiency anemia (drinking)When consumed, the Iron(II) ions in the water are said to be readily absorbed by the digestive tract, and iron-deficiency anaemia is listed among the drinking indications for iron springs.
Characteristic reddish-brown cloudy waterThe water's distinct color is the result of a chemical reaction. When dissolved Iron(II) ions are exposed to oxygen in the air, they oxidize into Iron(III) ions, creating the signature reddish-brown hue.

Iron ion Top 5 Hot Springs

Top 5 hot springs registered on this site with the highest content.

RANKING BY THIS MINERAL CONTENT

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References

SPRING TYPEMay 5, 2026· 1min read

Ferruginous Springs: Iron-Rich, Rust-Red Waters & Their Drinking Indication

Ferruginous springs contain iron ions (Fe²⁺ + Fe³⁺) at 20 mg/kg or more. Clear at the source, they turn reddish-brown or golden on contact with air. Iron-deficiency anemia is its official drinking indication.

SYMPTOMSMay 6, 2026· 2min read

Iron Springs & Iron-Deficiency Anemia | Drinking Indication & Precautions

Iron springs (含鉄泉) carry an official drinking indication for iron-deficiency anemia in Japan's Ministry of the Environment guidelines. Drinking spring water rich in ferrous ions (Fe²⁺) is believed to supplement dietary iron intake effectively.

MINERALMay 5, 2026· 2min read

Metasilicic Acid: The "Beauty Spring" Standard Mineral & Top 5 Onsen

Metasilicic acid (H₂SiO₃) is a natural moisturizer also found in skincare lotions. Hot springs containing more than 50mg/kg are called "beauty springs" — leaving skin hydrated long after bathing. This is one of the therapeutic spring criteria in Japan's Mineral Spring Analysis Guideline (Table 1-1).

Iron ion: Main Effects & Top 5