IRON

Iron ion: Main Effects & Top 5

Published May 5, 2026·1min read

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.

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 readily absorbed by the digestive tract. This can help supplement the body's hemoglobin synthesis, which is beneficial for this type of anemia.
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

References

SPRING TYPEMay 5, 2026· 1min read

Ferruginous Springs: Iron-Rich Waters for Anemia & Unique Rust-Red Baths

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. Indicated for drinking to help with iron-deficiency anemia.

SYMPTOMSMay 6, 2026· 2min read

Iron Springs for Iron-Deficiency Anemia | Drinking & Bathing Benefits Explained

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).