The brick may not be one crystal, but I'm willing to bet it could have a microcrystalline structure, which would lend itself to fracturing in somewhat geometrical shapes. I have often found, while walking along a streambed, rocks that resemble squares or rectangles, sometimes spheres.
If the martian rock was a brick, where are the other bricks? You can't make much with one brick.
If the martian rock was a brick, where are the other bricks? You can't make much with one brick.