PM2.5 Particles
                This is one view of PM2.5 particles on a Teflon air filter.
                  With the red plate the crystals can be seen to
                  have a positive sign of elongation.
              
              
                Transmitted Linear Polarized Light with the Red Plate
                
Definition/Function:
                Significance in the Environment:
                Characteristic Features:
                Associated Particles:
                References: