Holmium was discovered in 1878 by the Swiss chemists Marc Delafontaine and Jacques-Louis Soret, who spotted its unusual spectral lines while studying rare-earth minerals. In 1879, the Swedish chemist Per Teodor Cleve independently found it as an oxide hidden in a sample of erbium.
Cleve named the new element after his home city of Stockholm, whose Latin name is ‘Holmia’. Pure holmium metal was not produced until the 20th century, because it is very difficult to separate from the other rare-earth elements it is always found with.
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- Symbol: Ho
- Atomic Number: 67
- Atomic Weight: 164.93
- Element Classification: Lanthanide (rare-earth metal)
- Discovered By: Marc Delafontaine and Jacques-Louis Soret; Per Teodor Cleve
- Discovery Date: 1878
- Name Origin: Latin: ‘Holmia’, meaning Stockholm
- Density(g/cc): 8.79
- Melting Point: 1474°C
- Boiling Point: 2700°C
- Appearance: Bright, silvery-white metal
- Atomic Radius(pm): 176
Relation to Other Elements
Holmium is a member of the lanthanide series, the row of rare-earth metals near the bottom of the periodic table, sitting between dysprosium and erbium. Like the other lanthanides, it is a soft, malleable metal that slowly tarnishes in air and reacts with water. Holmium is remarkable for having the highest magnetic strength (magnetic moment) of any naturally occurring element, which makes it valuable for building some of the world’s strongest magnets.
Natural Occurrence
Holmium is one of the rarer lanthanides, making up only about 1.3 parts per million of the Earth’s crust. It is never found as a free metal. Instead, it occurs in small amounts in rare-earth minerals such as monazite, gadolinite and xenotime. Most of the world’s holmium is mined and refined in China, where it is separated from other rare-earth elements using a process called ion exchange.
Uses
Although holmium is rare, it has some special uses:
- Medicine: Holmium lasers are used by surgeons to break up kidney stones and to perform precise, minimally invasive operations.
- Magnets: Because of its extreme magnetic properties, holmium is used in pole pieces to focus the fields of the strongest magnets.
- Nuclear reactors: Holmium absorbs neutrons, so it can be used in control rods to help keep nuclear chain reactions in check.
- Colouring: Holmium oxide gives glass and cubic zirconia gemstones a yellow or red colour.
- Science: Holmium oxide solutions are used as standards to check the accuracy of laboratory instruments called spectrophotometers.
Holmium shows how even the rarest elements can play important roles in modern technology, from medical lasers to powerful magnets.