This rock is 2 3/8", weighs 71 grams has a density of 2.958,I tested the density a few times and its always 2.958, has a hardness of 6-7 almost clear streak test, I tested the streak again and I would say its clear and no color.Found this rock among cobble stones in Roscommon Ireland]3]3http://www.johnbetts-fineminerals.com/jhbnyc/articles/specific_gravity.htm
Your rock is likely to a metamorphic rock: metabasalt (metamorphosed basalt), ophiolite, or Amphibolite. Most basaltic rock when cut will show vugs or void spaces. Typical metamorphic rocks have few open voids due to the pressure and temperature changes which close these voids as the rocks are transformed. Texture of your stone suggests it is more likely to be metamorphic than basalt.
Metamorphic rocks are found in Ireland (see geological if Irealend).
Also, my experience with cutting and polishing rocks is most basaltic rocks (except for obsidian: volcanic glass) do not polish well because of the tiny voids.