The low temperature red form of mercuric iodide has been grown by a new chemical transport method which introduces organic monomers or polymers during the crystal growth process. Resulting crystals are in the form of platelets which are more directly useful in radiation detector device application. Platelets near one centimeter in width and 200 μm in thickness have been grown in periods of a few days using only 99.9% (unpurified) starting material. Measurements of X-ray and gamma ray energy resolution from detectors fabricated from platelets have yielded a 1.15 keV (FWHM) value for the 59.5 keV Am-241 line and 400 ev (FWHM) for the 5.9 keV Fe-55 line. These are again among the highest resolution values ever measured for HgI 2. Electrical carrier transport property values of HgI 2 so grown equal the best values previously measured from vapor grown material.