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A rare-earth metallic element. Holmium occurs naturally in rare-earth minerals such as gadolinite, monazite, and xenotime. Its abundance in the earth's crust is about 1.2 ppm. Holmium was discovered by Delafontaine and Soret in 1878 and independently by Cleve in 1879. Metallic holmium is a silver gray color and tarnishes slowly in air. Holmium is used as a catalyst and for some electronic applications.

Synonyms and Related Terms



  • Sensitive to air, light, and moisture.
  • Contact may cause irritation.
  • Fisher Scientific: MSDS

Physical and Chemical Properties

Soluble in dilute acids. Slightly soluble in water.

Composition Ho (atomic no. 67)
CAS 7440-60-0
Melting Point 1474 C
Density 8.7947 g/ml
Molecular Weight atomic wt = 164.9303
Boiling Point 2700 C

Resources and Citations

  • Web Elements: Website (accessed Dec. 15, 2004)
  • Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
  • Van Nostrand's Scientific Encyclopedia, Douglas M. Considine (ed.), Van Nostrand Reinhold, New York, 1976
  • Random House, Webster's Encyclopedic Unabridged Dictionary of the English Language, Grammercy Book, New York, 1997
  • The Merck Index, Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983 Comment: entry 4763
  • The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998