Two hafniums don’t make a holmium. This third member of the heavy rare-earth elements (HREE) has three electron pairs that give it the ability to be the leading medical laser, detect objects based on their vibrational signal, defeat infrared heat-seeking missiles, and generate high-energy laser pulses.
Ho:YAG solid state lasers are used in military and space-based laser distance and ranging (LADAR) systems to create 3D images and detect objects at great distances.
Laser-based Ho:YAG is used in infrared countermeasure (IRCM) systems to confuse shoulder-launched, infrared "heat-seeking" missiles firing at jets and helicopters.
Holmium: yttrium aluminum garnet (Ho:YAG) is the most widely used laser in medical surgical procedures.
Holmium coherent laser-based radar systems are used to detect hidden remote targets using high-resolution Doppler.
Thulium, Holmium:Yttrium Lithium Fluoride (Tm,Ho:YLF) lasers have space-based applications with high-pulse energies.
Holmium has the highest magnetic moment (10.6 µB) of any naturally occurring element and has been used to create the highest known magnetic fields as a pole piece or magnetic flux concentrator.
The element symbols for Carbon-Holmium-Cobalt-Lanthanum-Tellurium spells CHoCoLaTe.
Holmium is one of the colorants used in cubic zirconia, for use in jewelry, providing the dichroic colors of peach and yellow.
A glass multiband calibration filter (holmium- HY1) is made by Hoya glass.
Holmium was discovered by Swedish chemist, geologist, botanist, and hydrogapher Per Teodor Cleve in 1879.
He obtained an impure erbia from which scandia and ytterbia had been removed and noticed that the atomic weight of his impure erbia did not match that of erbia discovered by Carl Mosander in 1843.
He immediately started refining it by fractional crystallization into three "earths", erbia, holmia, and thulia.
Holmium and thulium were both new rare earths that Cleve verified by molecular weight and their spectral lines.
The spectra of the elements had previously been studied by Swiss chemists Marc Delafontaine and Jean-Louis Soret who called it "element X" but were not able to separate it (Weeks and Leicester, 1968, p. 681).
Holmium was named by P.T. Cleve for Holmia, the Latin name for the city of Stockkholm, which he described as "whose surroundings contain many minerals rich in yttria" (Cleve, 1879).
Holmium is a bright silver metal that is stable in dry air but oxidizes rapidly in moist air and at elevated temperatures.
The metal is relatively soft and is malleable.
It has a hexagonal close-packed structure, a density of 8.803 gm/cm3, a melting point of 1461 °C, and a boiling point of 2600 °C.
Holmium oxide, or holmia, occurs as a sesquioxide with the formula Ho2O3.
The oxide is a light yellow powder with a melting point of 2360 °C, a specific gravity of 5.0 gm/cm3, and a formula weight of 378.86.
Preparation of Metal
Holmium metal is typically prepared by calciothermic reduction of the trihalide, typically HoF3.
Although its melting point is similar to Y, Gd, Tb, and Lu, its vapor pressure at the melting point is much higher.
This makes purification of Ho, and similar elements Sc, Dy, and Er with high vapor pressures, comparatively easy.
Common interstitial impurities which form stable compounds with nitrogen, carbon, and oxygen remain in the residue when the metal is sublimed at 1220 °C at a slow rate (Beaudry and Gschneidner, Jr., 1978).
Holmium metal is formed when the fluoride preferentially separates from holmium fluoride at high-temperature and combines with calcium metal forming calcium fluoride and deposits a high-purity holmium metal.
Large resources of holmium in xenotime and monazite are available worldwide in ancient and recent placer deposits, uranium ores, and weathered clay deposits (ion-adsorption ore).
It occurs in the Earth’s crust at an average concentration of 1 parts per million.
Xenotime is enriched in holmium oxide and contains 2.0% to 2.6% of the rare-earth oxide (REO) content.
Monazite-(Ce), which is more abundant in the Earth’s crust than xenotime, has holmium oxide contents of 0.05% to 0.12% of the REO content.
The yttrium-enriched Longnan-type ion-adsorption ore has a holmium oxide content of 1.6% of the REO content, however, the Xunwu-type contains only a trace amount.
Hard rock monazite-(Nd) in the Lemhi Pass district of Idaho-Montana has an average holmium oxide content of 0.19% of the REO distribution (Hedrick, unpublished manuscript).
Holmium oxide contents in apatite, loparite, and eudialyte in Russia are 0.05%, 0.7%, and 2.9%, respectively (Hedrick, Sinha, and Kosynkin, 1997).
Only trace amounts of holmium oxide occur in bastnäsites at the Bayan Obo mine in China and at Mountain Pass in the United States.
Subeconomic resources of dysprosium occur in apatite-magnetite-bearing rocks, eudialyte-bearing deposits, deposits of niobium-tantalum minerals, non-placer monazite-bearing deposits, sedimentary phosphate deposits, and uranium ores, especially those of the Blind River District near Elliot Lake, Ontario, Canada, which contain trace amounts of holmium in brannerite, monazite, and uraninite.
Additional subeconomic resources in Canada are contained in allanite, apatite, and britholite at Eden Lake, Manitoba; allanite and apatite at Hoidas Lake, Saskatchewan; fergusonite and xenotime at Nechalacho (Thor Lake), Northwest Territories; and eudialyte-(Y), mosandrite, and britholite at Kipawa, Quebec.
It occurs in various minerals in differing concentrations and occurs in a wide variety of geologic environments, including alkaline granites and intrusives, carbonatites, hydrothermal deposits, laterites, placers, and vein-type deposits (Hedrick, 2010).
Xenotime and monazite is recovered from heavy-mineral sands (specific gravity >2.9) deposits in various parts of the world as a byproduct of mining zircon and titanium-minerals or tin minerals. Heavy mineral sands are recovered by surface placer methods from unconsolidated sands.
Many of these deposits are mined using floating dredges which separate the heavy-mineral sands from the lighter weight fraction with an on-board wet mill through a series of wet-gravity equipment that includes screens, hydrocyclones, spirals, and cone concentrators.
Consolidated or partially consolidated sand deposits that are too difficult to mine by dredging are mined by dry methods.
Ore is stripped by typical earth-moving equipment with bulldozers, scrapers, and loaders or by water jet methods.
Ore recovered by these methods is crushed and screened and then processed by the wet mill described above.
Wet mill heavy-mineral concentrate is sent to a dry mill for processing to separate the individual heavy-minerals using a combination of scrubbing, drying, screening, electrostatic, electromagnetic, magnetic, and gravity processes.
Vein monazite has been mined by hard-rock methods in South Africa and the United States (Hedrick, 2010).
Loparite is mined by underground methods using room and pillar methods.
Ore is drilled and blasted and removed from the mine.
The ore is then processed by the same hard-rock methods as applied to bastnäsite to make a loparite concentrate with a 0.7% Ho2O3 content.
In Kyrgyzstan, synchysite-(Y) with a Ho2O3 content of 0.8% was mined by hard-rock methods from the open-pit Kutessai-II deposit near Aktyuz.
Argillaceous marine sediments enriched in fossil fish remains at the Melovie deposit in Kazakhstan were previously recovered for their uranium and rare-earth content, including dysprosium.
The main source of the world’s holmium is the ion-adsorption lateritic clays in the southern provinces of China, primarily Fujian, Guangdong, and Jiangxi, with a lesser number of deposits in Guangxi and Hunan.
These deposits are mined by leaching methods (Hedrick, 2010).
Selected holmium-bearing minerals
Ion adsorption lateritic clays Y-enriched lateritic clays
Beaudry and Bernard J. and Karl A. Gschneidner, Jr., 1978, Preparation and Basic Properties of the Rare Earth Metals: chapter 2 in Handbook of the Physics and Chemistry of Rare Earths-Volume 1:Metals, (Gschneidner, Jr. and Eyring, editors), North-Holland, New York, p. 173-232.
Brauer, Georg, 1987, Story of RE names: chapter in 1787-1987 Two hundred years of rare earths, North Holland, New York, Rare-earth Information Center, Ames, Iowa, IS-RIC 10, 32 p.
Cleve, Per Teodor, 1879, Sur deux nouveaux éléments dans l’erbine [On two new elements with erbia]: Comptes Reudus, July 7, no. 1, p. 478-481.
Gschneidner, Karl A. Jr., 2011, The Rare Earth Crisis—The Supply/Demand Situation for 2010-2015: article in Material Matters, Aldrich Chemical Co., Milwaukee, Wisconsin, v. 6, no. 2, p. 34-35.
Hedrick, James B., 2010, Rare earths: chapter in Mineral commodity summaries 2010, U.S. Geological Survey, p. 128-129.
Hedrick, James B., 1990, Rare earths—The lanthanides, yttrium, and scandium: chapter in Minerals Yearbook 1990, U.S. Geological Survey, v. 1, p. 903-922.
Hedrick, James B., 1991, Rare earths—The lanthanides, yttrium, and scandium: chapter in Minerals Yearbook 1991, U.S. Geological Survey, v. 1, p. 1211-1237.
Hedrick, James B., Shyama P. Sinha, and Valery D. Kosynkin, 1997, Loparite—a rare-earth ore (Ce,Na,Sr,Ca)(Ti,Nb,Ta,Fe+3)O3: Journal of Alloys and Compounds, v. 250, p. 467-470.
Weeks, Mary E., and Henry M. Leicester, 1968, Discovery of the Elements (7th ed.): Easton, Pennsylvania, Journal of Chemical Education, 896 p.