from a sculptors point of view basalt is modestly challenging to work in comparison to other stones such a granite or sandstone , which are usually pretty predictable in their voice. It can be challenging to sound the stone ( tapping and listening for the stones voice that gives you a hint on how it is going to break as well visually seeing the voice ) and the tightness of the grain doesn't always split in how one would predict. In regards to cutting it's in the medium hard range. Dressing it from my perspective is totally delightful due to the internal and external color variation and how it takes on a totally different personality when texturized and or polished. We don't use columnar basalt for building walls normally. It is too expensive here. The columnar basalt is mostly used as sculptural elements and or sliced and textured and used as stepping stones ( quite beautiful when set into a hillside ) Regular native basalt field stone is regularly used in walling. From Hillside development

When exterior materials of different coefficients of expansion are rigidly attached to one another, they will eventually fail. Therefore, the attachment detail of veneer materials not only needs to allow water to drain, it must allow the materials to move independently. This is why the original "brick veneer" system had a cavity between the structural wall and a wythe of brick 4" thick and the brick was supported on a ledge and attached to the wall with flexible ties. A stone veneer wall was the same with 4" thick stone. I've designed and built many buildings with this system. Designing a tile-like cladding for a wood framed wall is difficult even in warm, dry climates. Some good systems were described in this thread 5 years ago. I'm not sure why cultured stone would perform worse than natural stone except that it absorbs more moisture, however, the joints do that anyway and in the photos above, the cultured stone doesn't appear to have cracked.

Our bedroom is 14' x 15' and I think that is the minimum I would want. We do have an armoire across from our bed and a queen size bed with two longish end tables but we are almost wall to wall on the bed wall. The proportion is what bothers me more - I would be afraid it will look like a bowling alley. I think the 20' is likely too long regardless of width - 16 or 18 would probably feel better and I would take the extra square footage and make it wider. . .

They are 9 1/2in square in the middle. Then the flange is 13in and then going to 11in right above the stone if that makes sense. We really wanted to get away from the tapered type of column that everyone is doing right now. I think square is very classic and does not 'date' the house to a particular fad.