Light blocks are 33.6% the mass of hull blocks per cubic cm and an equal mass with cargo bays. They have the same health, and cost the same price per cubic cm.
These blocks will cause a light sprite to appear above where the block is placed. These blocks can be oriented however the player wishes and the light sprite will follow the orientation the player selects. At the moment, scaling the light block will not affect the scale of the generated sprite.
These can be used on player stations to highlight docking ports more effectively. In sectors with dense fog, lights can be seen effectively at a long distance. Players can put them on their ships and be able to see them much easier. You can increase the intensity by building a 2x2x2 box of light blocks as small as possible to make them even clearer in fog.