Mineral:  Alunite (ammonioalunite) NH4Al3(SO4)2(OH)6

Sample No.: alunite.1

Locality:  Synthetic.

XRD Analysis:  The five strongest X-ray diffraction lines for this new 
mineral are (d angstrom (Irel)(hkl)): 3.023 (100) (113); 5.04 (93) (012); 2.996 
(50) (021); 1.917 (32) (303); and 2.53 (31) (205) (S. Altaner, 
unpublished data.)

Chemistry: Chemical analyses by USGS Analytical Laboratory, Reston, 
showed that this synthetic NH4-alunite has high H2O and low Al and 
NH4 contents, yielding the following chemical formula:  (NH4).81 
(H3O).19 [A12.72 (SO4)1.95 (H2O).75 (OH)5.26], assuming 
electrostatic neutrality and that excess H2O exists as H3O+ and as 
H2O in AlO2(OH)4 octahedra (S. Altaner, unpublished data.)

Conditions of Synthesis:  Na-, K- and NH4- alunites were prepared 
from Fisher-certified ACS reagent Al2(SO4)3.nH2O and Na2SO4, 
K2SO4 or (NH4)2SO4, respectively, in the mole ratio 4:1.  
Approximately 30 g of solid reagent was heated with 150 ml 
deionized water in a teflon-lined autoclave at 150¡ C for 3 days.  The 
alunite product was rinsed by boiling in deionized water for 2 hours. 
Synthesis in this manner produces alunites with considerable 
substitution of hydronium for Na+ . K+ or NH4+ in the structure.  In 
order to exchange the hydronium with Na+, K+ or NH4+,  the alunites 
were heated in gold-lined Morey bombs to 300¡ C in 1.0 molar 
Na2SO4, or saturated K2SO4, for a period of two weeks.  The products 
were again rinsed by boiling in deionized water for 2 hours.  
Comparison of the spectra of the alunites so prepared to that of 
natural alunite suggests that the synthetics still contain some water.

NO SOLID OR POWDERED SAMPLE AVAILABLE FOR REFLECTANCE
