Pearlstone Brick is a building material. They do not spread The Hallow when placed, therefore making them a safer construction material than their raw ingredients.
While pickaxes prior to the Nightmare and Deathbringer Pickaxes are unable to mine Pearlstone Bricks, they have no special resistance to explosions.
Like any bricks with low saturation, Pearlstone Bricks can only be painted with deep colored paints, black or white. This also applies to their wall variation.