The cover photo for the 1997 Journal of Petrology was made by S. A. Morse of a thin section from a sample provided by Dr. H. S. Yoder, Jr., of the mineral yoderite. This unique occurrence, at Mautia Hill, Tanzania, was a product of high pressure metamorphism of a Mg‑Al rich "whiteschist". The photo shows the reaction of Kyanite + Talc + Hematite to Yoderite + Quartz (see Fockenberg and Schreyer, 1994, J. Petrology 35, 1341‑1375). The cover photo represented an average blue color for the yoderite, taken in plain light without the lower polar. The images below are taken with the lower polar in two different orientations, to show the pleochroism of this mineral. This particular section does not show quite the complete range of the pleochroic colors, which my experimental mentor, the late Hat Yoder, always liked to describe as "passionate purple to boudoir pink", but the blue and pink images shown here come fairly close to the endmember colors.
The cover photo for the 1998 Journal of Petrology was furnished by my good friend James
Scoates; it is of a zoned, iridescent labradorite from the Chugwater anorthosite, Wyoming. I
mention this as an advertisement for anorthosites in general, as a salute to our collaboration in
rescuing the JP cover from muddy images of less interesting rocks, as an incentive to others to
do the same, and most importantly, to point out that equally spectacular zoned labradorites occur
(of course!) in the Nain anorthosite of Labrador.