One of the usual methods of building breakwaters in Iran is to use rock mass structures. Most of the rocks in the south of Iran are sedimentary (limestone, sandstone and lomashell). Most of the regulations in present codes regarding the usage of stone in hydraulic protection structures in other countries are mostly according to the availability and abundance of igneous rocks, as well as their own specific different geological conditions, so they have criteria’s that are more suitable for these types of rocks. In 2009, the regulations for the use of stone in breakwaters and protection structures were prepared to provide a codified standard for quality control during construction due to the extreme poverty of desirable stones in the south of Iran. Despite the promulgation of this regulation , the quality of construction in the majority of rock mass structures is still not favorable, the reasons for which can be attributed to: high abundance of harmful clay minerals within the range of extractable depth of the existing formations, high heterogeneity in the quality of the extracted rock, The extension of the life of the constructed structures beyond the initial assumptions of the design, the insufficiency of the existing standards for medium and long term serviceability, and in general the dominant effect of mineralogy on the overall performance of sedimentary rocks in rock mass structures . With regard to the mentioned cases, in this article, a new criterion for the classification of sedimentary rocks has been proposed.