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Hydrotalcite with serpentine, Snarum, Modum, Buskerud, Norway. Size: 8.4 x 5.2 x 4.1 cm
CategoryCarbonate mineral
(repeating unit)
Strunz classification5.DA.50
Crystal system3R polytype: Trigonal
2H polytype: Hexagonal
Crystal class3R polytype: Hexagonal scalenohedral (3m)
H-M symbol: (3 2/m)
2H polytype: Dihexagonal dipyramidal (6/mmm)
Space groupR3m
Unit cella = 3.065 Å,
c = 23.07 Å; Z = 3
ColorWhite with possible brownish tint
Crystal habitSubhedral platey crystals, lamellar-fibrous, rarely euhedral prismatic; commonly foliated, massive
Cleavage{0001}, perfect
TenacityFlexible, not elastic
Mohs scale hardness2
LusterSatiny to greasy or waxy
Specific gravity2.03 - 2.09
Optical propertiesUniaxial (-)
Refractive indexnω = 1.511 - 1.531 nε = 1.495 - 1.529
Birefringenceδ = 0.016
Other characteristicsGreasy feel
References[1][2][3] [4]

Hydrotalcite is a layered double hydroxide of general formula Mg
), whose name is derived from its resemblance with talc and its high water content. The layers of the structure stack in multiple ways, to produce a 3-layer rhombohedral structure (3R Polytype), or a 2-layer hexagonal structure (2H polytype) formerly known as manasseite. The two polytypes are often intergrown.[1][2][4] The carbonate anions that lie between the structural layers are weakly bound, so hydrotalcite has anion exchange capabilities.

It was first described in 1842 for an occurrence in a serpentine - magnesite deposit in Snarum, Modum, Buskerud, Norway.[1] It occurs as an alteration mineral in serpentinite in association with serpentine, dolomite and hematite.[2]


Nuclear fuel reprocessing[edit]

     Hydrotalcite has been studied as potential getter for iodide in order to scavenge the long-lived 129I (T1/2 = 15.7 million years) and also other fission products such as 79Se (T1/2 = 295 000 years) and 99Tc, (T1/2 = 211 000 years) present in spent nuclear fuel to be disposed under oxidising conditions in volcanic tuff at the Yucca Mountain nuclear waste repository. Carbonate easily replaces iodide in its interlayer. Another difficulty arising in the quest of an iodide getter for radioactive waste is the long-term stability of the sequestrant that must survive over geological time scales.

Anion exchange[edit]

Layered double hydroxides are well known for their anion exchange properties.


Hydrotalcite is also used as an antacid.

Wastewater treatment[edit]

Treating mining and other wastewater by creating hydrotalcites often produces substantially less sludge than lime. In one test, final sludge reductions reached up to 90 percent. This alters the concentration of magnesium and aluminum and raises the pH of the water. As the crystals form, they trap other waste substances including radium, rare earths, anions and transition metals. The resulting mixture can be removed via settling, centrifuge, or other mechanical means.[5]

See also[edit]


  1. ^ a b c Mindat.org
  2. ^ a b c Handbook of Mineralogy
  3. ^ Webmineral data
  4. ^ a b IMA Nomenclature Report
  5. ^ Hoopes, Heidi (June 12, 2014). "Wastewater that cleans itself results in more water, less sludge". www.gizmag.com. Retrieved 2016-06-11.
  • Douglas, G., Shackleton, M. and Woods, P. (2014). Hydrotalcite formation facilitates effective contaminant and radionuclide removal from acidic uranium mine barren lixiviant. Applied Geochemistry, 42, 27-37.
  • Douglas, G.B. (2014). Contaminant removal from Baal Gammon acidic mine pit water via in situ hydrotalcite formation. Applied Geochemistry, 51, 15-22.

Further reading[edit]

  • Jow, H. N.; R. C. Moore; K. B. Helean; S. Mattigod; M. Hochella; A. R. Felmy; J. Liu; K. Rosso; G. Fryxell; J. Krumhansl (2005). Yucca Mountain Project-Science & Technology Radionuclide Absorbers Development Program Overview. Yucca Mountain Project, Las Vegas, Nevada (US).
  • Kaufhold, S.; M. Pohlmann-Lortz; R. Dohrmann; R. Nüesch (2007). "About the possible upgrade of bentonite with respect to iodide retention capacity". Applied Clay Science. 35 (1–2): 39–46. doi:10.1016/j.clay.2006.08.001.
  • Krumhansl, J. L.; J. D. Pless; J. B. Chwirka; K. C. Holt (2006). Yucca Mountain Project getter program results (Year 1) I-I29 and other anions of concern. SAND2006-3869, Yucca Mountain Project, Las Vegas, Nevada.
  • Mattigod, S. V.; G. E. Fryxell; R. J. Serne; K. E. Parker (2003). "Evaluation of novel getters for adsorption of radioiodine from groundwater and waste glass leachates". Radiochimica Acta. 91 (9): 539–546. doi:10.1524/ract.91.9.539.20001.
  • Mattigod, S. V.; R. J. Serne; G. E. Fryxell (2003). Selection and testing of getters for adsorption of iodine-129 and technetium-99: a review. PNNL-14208, Pacific Northwest National Lab., Richland, WA (US).
  • Moore, R. C.; W. W. Lukens (2006). Workshop on development of radionuclide getters for the Yucca Mountain waste repository: proceedings. SAND2006-0947, Sandia National Laboratories.
  • Pless, J. D.; J. Benjamin Chwirka; J. L. Krumhansl (2007). "Iodine sequestration using delafossites and layered hydroxides". Environmental Chemistry Letters. 5 (2): 85–89. doi:10.1007/s10311-006-0084-8.
  • Stucky, G.; H. M. Jennings; S. K. Hodson (1992). Engineered cementitious contaminant barriers and their method of manufacture. Google Patents.