Remnant of cast rodinium
In metallurgy, casting was the process of pouring molten metal into a predetermined shape.
The Earth Outpost Stations located along the Romulan Neutral Zone were constructed with a protective shield made out of cast rodinium, a material which Spock claimed in 2266 was the hardest substance known to their science. (TOS: "Balance of Terror")
While investigating an ancient starship the originally constructed by a species of ancient insectoid, Montgomery Scott took notice of the ship's form of construction. He explained that "[t]his metal, it isn't cast or rolled," but in fact "[i]t was drawn into filaments and spun." (TAS: "Beyond the Farthest Star")