a small, columnlike formation in a rock deposit, usually composed of limestone with grooved or scratched sides
See stylolite in American Heritage Dictionary 4
sty·lo·lite
noun
A secondary structure found along contacting surfaces of adjacent calcareous rock layers, the contact zone appearing in cross section as a series of jagged interlocking up-and-down projections that resemble a suture or the tracing of a stylus.
Origin: Greek stūlos, pillar; see stylite + -lite.