Previous classifications of sandstones are applicable at the petrographic level, but normally cannot be used with a hand specimen. This is particularly apparent with sandstones which contain a notable amount of relatively unstable rock fragments, such as chert, volcanic rocks, metamorphic fragments, and weathered feldspar. This field classification groups such components on the basis of color, but permits some further distinction between quartz and other light-colored grains if possible. A ternary diagram is used with the 3 points being: quartz and quartzite, feldspar and pale to colorless rocks, and dark-colored rocks and minerals. Subdivisions possible are: quartzose, leucocratic, mesocratic, and melanocratic.