A transparent yttrium aluminum garnet precursor composition is provided that includes a plurality of calcined particles of yttrium aluminum oxide having a mean particle domain size of between 10 and 200 nanometers and a predominant hexagonal crystal structure. High levels of YAG transparency are obtained for large YAG articles through control of the aluminum:yttrium atomic ratio to 1:06.+-.0.001 and limiting impurity loadings to less than 100 ppm. The composition is calcined at a temperature between 700.degree. Celsius and 900.degree. Celsius to remove organic additives to yield a predominant metastable hexagonal phase yttrium aluminum oxide nanoparticulate having an atomic ratio of aluminum: yttrium of 1:0.6.+-.0.001. With dispersion in an organic binder and a translucent YAG article is formed having a transmittance at a wavelength of 1064 nanometers of greater than 75%. The translucent YAG article is characterized by an average domain size of less than 1 micron and having a density of at least 99% and inclusions present at less than 2 surface area percent. The ability of a batch of yttrium aluminum oxide nanoparticles to serve as a transparent YAG precursor includes collecting an X-ray fluorescence spectrum from a plurality of aluminum oxide nanoparticles having a predominant crystal structure other than garnet to yield an A1:Y raw integrated peak intensity ratio. The nanoparticles are sintered to yield a predominant garnet phase and a secondary phase and optionally isostatic pressing during sintering. By using only precursor nanoparticles with a standard deviation of .+-.0.003 in the peak ratio exceptionally high transparency YAG is reproducibly produced.