Númenórean brick can be found naturally in most Umbaric structures, and crafting materials found all over Mordor.
Stairs, pillars, slabs and two carved variants can also be crafted and found naturally.
Gondor bricks and their black counterparts have a gulduril variant. These cannot be crafted, but are created by right-clicking their respective block with a piece of gulduril. This creates a green shimmering effect around the block, useful for buildings like Minas Morgul and other haunted-like builds.
This brick was first added as 'Black Gondor Brick' in Public Beta 22, craftable on the Gondorian crafting table. However, in Update 34 (with the addition of Umbar), the brick was renamed to be used by both Gondor and Umbar.
The gulduril variants were added in Public Beta 27.