The polarizing microscope as an analytical tool across the science curriculum. William Nicol invented the first polarizing microscope in the mid-nineteenth century and was the first to use it as an analytical tool. Nicol used his invention to study thin layers of birefringent crystals such as calcite and quartz and found that he could identify minerals by observing their optical properties under the microscope.
Birefringent crystals have two indices of refraction and thus produce two beams of polarized light.
In 1928, E.H. Land invented a process for producing films for the polarizing microscope by embedding birefringent crystals in plastic. The use of polarizing films has led to the wide use of the polarizing microscope in industrial and medical research during the last 50 years. Today, the polarizing microscope still plays an important role in the analytical laboratory. Polarizing microscopes are more effective than light microscopes for studying colorless crystals. They also make it easier to observe irregularities and cracks in the crystals.