Erbium - Er
Erbium (Er)
Erbium is a soft, silvery lanthanide metal that slowly tarnishes in air and reacts with water. It occurs with other rare-earth elements in minerals including monazite and bastnäsite.
| Atomic number | 68 |
|---|---|
| Standard atomic weight | 167.259 |
| Electron configuration | [Xe] 4f12 6s2 |
| Density | 9.07 g/cm3 |
| Melting point | 1529 °C |
| Boiling point | 2868 °C |
| Common oxidation state | +3 |

Uses and applications
Erbium compounds colour glass and ceramics pink. Erbium-doped optical fibres amplify signals in fibre-optic communications, and erbium-doped crystals are used in lasers.
Erbium and water treatment
Erbium is not a routine water-treatment reagent. It may be present in water and residues associated with rare-earth mining, separation, and recycling; management depends on the chemical form and site-specific process-water composition.
Occurrence and environmental context
Erbium is recovered from rare-earth minerals, commonly through processes that separate chemically similar lanthanides. Environmental behaviour depends on its chemical form, solubility, and interactions with minerals and dissolved substances in water and soil.
Health and safety
Health risks depend on the particular erbium compound and exposure route. Avoid inhaling dust, consult the relevant safety data sheet, and use appropriate occupational controls when handling metal or compounds.
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Sources and further reading
Element page last reviewed: 24 October 2026 by Lenntech.