Caryopilite is reddish-brown to tan in color naturally; in thin sections, it is light brown to yellow.

The crystal structure shows some short-range order, but linkages between islands are fully disordered.

The name is derived from the Greek words κάρυον or "walnut", in reference to the mineral's brown color and crystal habit, and πΐλος or "felt", for its appearance under a microscope.

[7] In 1917, Gust Flink discovered a mineral he named ectropite (also spelled ektropite) that was most closely related to caryopilite.

[12] As of 2012[update], caryopilite has been found in Austria, Canada, China, France, Italy, Japan, New Zealand, Norway, Romania, Russia, Slovakia, South Africa, Sweden, the UK, and the US.