Can any rock be base rock?

[marcingo]

I had a 55 gal mixed reef. Due to being a student I couldn't afford all that live rock so I purchased Tufa rock from the local rock yard, boiled it and used it as my live rock. I then seeded it with about 20% real live rock. The tank did great for a year before I sold off and had to move. The only down side of Tufa rock is it is dense and does not look as good as real base rock which is just dead live rock.