From Wikipedia, the free encyclopedia
Jump to: navigation, search
Category Silicate mineral
(repeating unit)
Strunz classification 9.FA.30
Crystal system Monoclinic
Crystal class Prismatic (2)
or sphenoidal (2/m)
Unit cell a = 8.57 Å, b = 13.03 Å,
c = 7.18 Å; β = 112.73°; Z = 4
Color Colorless
Crystal habit Compact masses replacing plagioclase as pseudomorphs
Cleavage Good on {001}, distinct on {010}
Tenacity Brittle
Luster Vitreous
Diaphaneity Transparent to translucent
Specific gravity 2.32
Optical properties Biaxial (+)
Refractive index nα = 1.530 nβ = 1.531 nγ = 1.534
Birefringence δ = 0.004
2V angle Calculated: 60°
References [1][2][3]

Buddingtonite is an ammonium feldspar with formula: NH4AlSi3O8 (note: some sources add 0.5H2O to the formula). It forms by hydrothermal alteration of primary feldspar minerals. It is an indicator of possible gold and silver deposits, as they can become concentrated by hydrothermal processes. It crystallizes in the monoclinic crystal system and is colorless to white with a vitreous luster. Its structure is analogous to that of high sanidine (KAlSi3O8). Buddingtonite has a hardness of 5.5 and a specific gravity of 2.32.

Buddingtonite was discovered in 1964 at the Sulfur Bank mine near Clear Lake in Lake County, California (Erd et al., 1964). Clear Lake is at the north end of The Geysers geothermal area. It also occurs in the Tonopah, Nevada (Felzer et al., 1994) area and in hydrothermal areas in New Zealand (Yang et al., 2001) and Japan. It has also been reported from the sedimentary Phosphoria Formation in Idaho (Gulbrandsen, 1974), South Dakota (Solomon & Rossman, 1988), Wyoming, and Montana. It occurs in the oil shale deposit, near Proserpine, Queensland, Australia (Loughan, et al., 1983).

It was named for Arthur Francis Buddington (1890–1980), a petrologist at Princeton University.


  • Erd RC, White DE, Fahey JJ, Lee DE (1964). "Buddingtonite, an ammonium feldspar with zeolitic water". American Mineralogist. 49 (7–8): 831–50. 
  • Felzer B, Hauff P, Goetz AFH (1994). "Quantitative reflectance spectroscopy of buddingtonite from the Cuprite mining district, Nevada". Journal of Geophysical Research. 99 (B2): 2887–95. Bibcode:1994JGR....99.2887F. doi:10.1029/93JB02975. 
  • Gulbrandsen RA (1974). "Buddingtonite, ammonium feldspar, in the Phosphoria Formation, southeastern Idaho". USGS Journal of Research. 2 (6): 693–7. 
  • Loughan FC, Roberts FI, Linder AW (1983). "Buddingtonite (NH4-feldspar) in the Condor Oilshale Deposit, Queensland, Australia". Mineralogical Magazine. 47 (344): 327–34. doi:10.1180/minmag.1983.047.344.07. 
  • Solomon GC, Rossman GR (1988). "NH4<super>+</super> in pegmatitic feldspars from the southern Black Hills, South Dakota". American Mineralogist. 73: 818–21. 
  • Yang K, Browne PRL, Huntington JF, Walshe JL (2001). "Characterizing the hydrothermal alteration of the Broadlands-Ohaaki geothermal system, New Zealand, using short-wave infrared spectroscopy". Journal of Volcanology and Geothermal Research. 106: 53–65. Bibcode:2001JVGR..106...53Y. doi:10.1016/S0377-0273(00)00264-X. 
  • Voncken JHL, van Roermund HLM, van der Eerden AMJ, Jansen JBH, Erd RC (1993) Holotype buddingtonite, an ammonium feldspar without zeolitic H2O. American Mineralogist, 78, 204-209