Basalz Rods are mob drops added by Thermal Foundation. They are sometimes dropped when a Basalz is killed. Essentially, they are the Basalz equivalent of Blaze Rods.
Basalz Rods only have a single use: they can be crafted or pulverized into Basalz Powder. This material is a critical ingredient for creating Petrotheum Dust and, ultimately, Tectonic Petrotheum.