Gray Brick

Gray Brick is the neutral gray of the game, which makes it the default for anything meant to read as structure rather than decoration: castle walls, chimneys, foundations, the outer shell of a base. It sits quietly next to almost every other block, so it is a safe thing to build with before you have settled on a palette.

Moss will spread onto it and can be planted on it, which is the one mechanical quirk worth knowing. A moss farm does not have to be raw stone, so you can grow a colored moss wall as part of a finished room instead of leaving a patch of ugly natural blocks in the middle of your build.

Gemcorns are the exception. They insist on real stone and will refuse the brick, so a gem tree farm has to sit on ground you left unconverted.