unknown sedimentary rock

This rock is comprised of fine grain crystals but also features numerous pores and openings throughout it. The porous texture makes the rock feel rough to the touch despite the fine grain crystals. While the rock resembles igneous volcanic rocks like pumice or tuff it is not igneous; the rock is fully sedimentary as evidenced by the fact that when a drop of acid is placed upon it the rock effervesces (fizzes and bubbles). Thus, the fine crystals are likely calcite or a similar mineral. This rock doesn't contain any fossils but rocks of this type can at times contain them. The rock also does not taste salty. This carbonate rock was not formed in an oceanic environment. It was produced in the fresh [non-salt] ambient temperature waters long ago. rocksandminerals CC BY(4.0) via sketchfab [https://creativecommons.org/licenses/by/4.0/legalcode]