How to distinguish argillaceous limestone, argillaceous shale and mudstone?

Muddy limestone, mainly limestone, with mud content of 10%~40%.

Mud shale is mudstone, which may contain fine sand.

Mudstone generally refers to pure mudstone.

Difference: Limestone bubbles when acid is added dropwise, but there are still many dark residues. Mudstone and shale basically do not foam.

In terms of bedding, shale grain bedding is developed, and its grain size is coarser than mudstone. The others are not easy to distinguish.

In addition, shale is not a standardized concept.