gems, conservation, light stability, color science, museum conservation

In a discussion on the preservation of art objects it was pointed out that: . . .the ideal environment. . .would consist of an unilluminated region with cool constant temperature and a low constant humidity. When objects are stored in such an environment, as has happened in Egyptian tombs with their treasures and in European caves with their wall paintings, thousands of years can pass without significant deterioration; unfortunately, such conditions do not permit us to view the objects!! To the curator of art and artifacts incorporating organic dyes or organic vehicles containing pigments, this is a dominant consideration in his activities, while the curator of minerals and gems has, on the face of it, much less serious problems. The surprisingly extended listings in the Tables 2.3, 2.4 and 2.5 and the equally astonishing lack of adequate reviews in the literature nevertheless indicate that such complacency cannot be justified. For an extended discussion on this subject, refer to Pearl,23 and King.* These authors rely heavily on older work by Parsons® and Bannister.° There is a partial listing of light-sensitive minerals by Sinkankas’ and there are relevant sections in Nassau.!* There are undoubtedly many pertinent observations in the voluminous descriptions of individual minerals from varied localities in the literature, yet there appears to be no direct way to locate such data within a reasonable timeframe. The writer will welcome comments on significant omissions and errors from readers.