A boundstone is a special type of carbonate rock in the Dunham classification.
In the original classification by Dunham (1962),[1] boundstones are defined as "carbonate rocks showing signs of being bound during deposition [...].
The term "boundstone" is retained for authochthonous limestones in which the specific mode of organic binding cannot be recognized.
[4] Lokier and Al Nunaibi (2016)[5] define boundstone as "an autochthonous carbonate-dominated rock in which there is any form of evidence that the original components were organically bound at the time of deposition; however, the mode of binding is not identifiable.
"[6] In contrast to Embry and Klovan, they do not subdivide boundstones into smaller classes.