Crystals for polarimetry were mounted between glass in a 1:1 mixture of immersion oil (RI = 1.7) and DMF to minimize scattering at interfaces. The microscope design is described elsewhere, based on previous efforts. In short, continuous rotation of a pair of quarter-wave plates, with respect to stationary linear polarizers, generates a smoothly varying, time-dependent intensity signal that is demodulated to recover M, a sixteen-element transformation matrix that relates the polarization state of an incident beam of light, expressed as a four-element Stokes vector S, to its corresponding output vector: Sout = MSin. Data are displayed as a 4 × 4 array of images representing the spatial variance of one of the elements Mij of the matrix (normalized by M11). The microscope was built from a Zeiss ZM1 inverted microscope to which the home made mechanical modulators were added in the transmitted light path before and after the sample.