# What is this blue rock?

I am trying to identify a rock my husband found.The rock was found in Columbus Ohio about 20 feet (6 m) down. It is about the size of a basketball and extremely heavy (90 lbs) and difficult to cut into (3 diamond partner saw blades were only cut an inch into the rock). There are very smooth and very rough areas on the surface. It is mainly blue and white but there is also a bit of green here and there. All over the surface are pockets of crystals that are clear/sky blue/algae green. I have been trying for almost 15 years to find out what it is.

Additionally... when my husband's crew found it they were so curious about what the inside looked like they tried to cut it in half with a partner saw using a diamond blade. They ruined 3 blades and the saw and only got about an inch into the surface.

A full set of pictures is available here.

Very interesting pictures. I will go out on a limb and say it looks like it is mostly barite (barium sulfate, $\ce{BaSO_4}$). The clear ball-shaped crystals may be celestite (strontium sulfate, $\ce{SrSO_4}$). Barite often forms tabular crystals and is very dense. It is used in drilling mud for oil wells because it can help hold in the pressure. The sedimentary basin brine found in Pennsylvania and Ohio has quite a bit of barium and strontium so the sulfates could form. Maybe others can weigh in.