isotropic Applied to substances whose optical or other physical properties are the same from whatever direction they are observed. In thin-section and polished-section microscopy, an isotropic mineral has only one refractive index or one reflectance value respectively, whatever the orientation of the mineral as indicated in crossed polars. The beam of light is not split into two vibration directions, therefore, but passes through or is reflected off the mineral with no change in its optical characteristics.

isotropic Applied to substances whose optical or other physical properties are the same from whatever direction they are observed.