Advances have been made in the processing of mercuric iodide (HgI 2) used to make gamma-ray spectrometers. Refinements in purification methods, including the in-house synthesis of starting material, has resulted in a greatly increased yield of gamma-ray detectors exhibiting good energy resolution. Spectrometers of 2-3 mm thickness and 2.5×2.5 mm 2 area are produced which frequently exhibit energy resolutions of 3-8% FWHM at 662 keV. Spectral data is presented along with a table showing improved yields of these detectors for different starting materials. A correlation between spectrometer performance and charge transport data is presented which suggests that improved spectrometer performance is tied to increased hole transport.