Heat treatment produces a rich and distinctive, deep red color, and may produce a waxy or almost glassy texture. Otherwise, the texture is generally chalky. Normally homogeneous in appearance, but may be somewhat mottled. The range of characteristics of this material is limited. The translucent variety shows much greater variation, even within individual cobbles.
Color ranges from golden brown to pale brown, yellow, white and colorless.
Patterning varies from homogenous to mottle. Many pieces even have an appearance which strongly resembles quartzite. Microscopic examination, however, reveals that the material does not actually contain grains and is not a quartzite. In the translucent variety, transmitted light will be golden yellow in all but the more translucent, colorless pieces. Their ultimate origin is not clear.