Forms series with Andradite, with Hydrogrossular, with Uvarovite. See additional spectra of grossular garnets in library for comparison. This sample has been washed in HCl acid to remove carbonate contaminants.
Most grains are isotropic with parting surfaces.
Trace contaminant could be feldspar because of low interference color and possible twinning. Optical properties are consistent with this sample being nearly pure garnet.