The “Michel-Lévy Birefringence Chart” used in McCrone Associates’ The Particle Atlas (31) and in the McCrone Research Institute’s Polarized Light Microscopy (32) (Figure 25) is based on the Zeiss chart (Figure 4), except that the names of the minerals are not as numerous, and now a variety of other kinds of entries appear, including natural and synthetic fibers, chemicals, food products, and drugs, better reflecting the use of the chart by analytical microscopists in industry and government, rather than by mineralogists and petrologists.  Another version of the chart used for teaching purposes by the McCrone Research Institute is shown in Figure 26; this is the full Zeiss chart (Figure 4), which has been modified by indicating the birefringence qualitatively as low, moderate and high.  Different texts have different ranges, but here they are low = 0–0.010, moderate = 0.010–0.050, and high = >0.050.

click image to view large PDF version (567K) figure 25 click image to view large PDF version (653K) figure 26

Almost all of the manufacturers of polarizing microscopes have, at one time or another, supplied separate interference color charts for ready reference near the polarizing microscope.  Figure 27 is a vest-pocket-sized “Polarisation Colour Scale” supplied by Swift (England) over 50 years ago; it’s one of the very few charts that show the interference colors seen between parallel polarizers.

The Zeiss “Michel-Lévy Color Chart” (Figure 4) has already been described.  This beautiful chart was issued as a reprint in 1963, I believe; it accompanied an article by Joseph Gahm in Zeiss’ Werkzeitschrift No. 46 (14).  In this article, we learn from a footnote that the color chart was repainted by Mr. René Babillotte, and that the engravers were Meyle and Mueller, of Pforzheim, Germany [note: repainted 75 years after the original 1888 painting!].