Yep on our property. Very hard, steel knife won't scratch. doesn't Dumortierite have signature black spots? None on this. Very smooth, kind of looks like flint in a way, but not. Also sometimes has cream colored veins funning through it, but not always.
I have seen stuff like this up our way.
We have a LOT of old iron forges here and the slag from them comes in all different colors and textures.
From "glasslike" in clarity and appearance to pumice looking stuff and every color / texture combination out there.
But it could be natural too,,, they are a cool blue color for sure.
Hit
After researching on internet, it might be sodalite because of the cream vein in some. As far as I know, we don't have any sodium around here though. Although who can say. We've got a real mixed up mess with all the colors in a rainbow, yellow, blue, red, green, purple. Maybe some titanite.
They're all being shipped to a geologist at bureau of mines&minerals in a few days. Hopefully he will know. Need to soak some in acid first to get rid of iron stains. Not these though as no iron noticeable. Some others that look like citrine or topaz possibly. So should know in a few weeks.