Color in Feldspars
Anne M. Hofmeister and George R.
Rossman
Division of Geological and Planetary
Sciences
California Institute of Technoogy
Pasadena, CA 91125
Abstract
Pure feldspar, free of exsolution, is colorless. However, minor
chemical substituents, inclusions, interference effects from exsolution
lamellae, and radiation damage can produce color in the mineral.
Chemical impurities pro-
duce the yellow color of sanidine, orthoclase and calcic plagioclase,
the blue to green colors of amazonite, and the blue-green color of
sodic plagioclase. Inclusions create a wide variety of colors: pink,
brick-red, and grays are
common; orange, tan and green may also occur. Aventurine and shiller
effects also result from inclusions. Radiation produces gray or smoky
colors. Exsolution phenomena and oriented intergrowths produce
interference colors, schiller and chatoyancy. This chapter describes
the colored varieties of feldspar and their absorption spectra and
coloration mechanisms.
last
updated: l3-Jul-2023