This is a truly massive piece of amygdaloidal vesicular basalt, which are also known by the commercial name of "Galaxy Stone." Why? Because the vision of colourful vesicles of chalcedony, quartz, rhyolite, jasper, and other minerals look like little round and oval planets set into the black space which is the basalt. 
 
I picked this galaxy stone up in South Ayrshire on a rock hunting trip of Scotland away back in the early days of TSC. Mayber 2021 or 22. I picked it up because it was massive, shaped so satisfyingly as a giant oval itself, and had one big vug of chalcedony in the centre of it that looked like an eyeball looking back at me. 
 
The planets/vugs/vesicles in this vesicular basalt are white and pink. They are mainly made of chalcedony, jasper, and maybe rhyolite. The basalt is just basalt. This is an excellent rock for those that want to slice a galaxy stone and make cabochons or polish it. If you slice this horizontally you will get multiple pieces. I reckon I could get 11 slices even if a couple broke.
 
What is Vesicular Amygdaloidal Basalt?
 
Amygdaloidal refers to the basalt and how it cooled very slowly under certain conditions. Vesicular refers to the fact that it has little bubbles in it which remained after the lava cooled into basalt. The bubbles become planets or vugs when they are filled in over time with sediment. So the basalt is igneous because it is slow colled lava, but the vugs are sedimentary, filled by mineral rich groundwaters seeping into the bubbles over time.